It’s about weed control…at best.

When weeding, the best way to identify a weed and a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant. ~Author unknown

Weed control is the botanical component of pest control, which attempts to stop weeds, especially noxious or injurious weeds, from competing with desired flora and fauna, this includes domesticated plants and livestock, and in natural settings, it includes stopping non local species competing with native, local, species, especially so in reserves and heritage areas.

A plant is often termed a “weed” when it has one or more of the following characteristics:
a. Little or no recognized value (as in medicinal, material, nutritional or energy)
b. Rapid growth and/or ease of germination
c. Competitive with crops for space, light, water and nutrients

Weeds compete with productive crops and garden plants, ultimately converting productive land into an unmanageable scrub. Weeds can be poisonous, distasteful, thorny and interfere with the management of desirable plants.  Weeds compete with crops for space, nutrients, water and light. Smaller, slower growing seedlings are more susceptible than those that are larger and more vigorous. Weeds also vary in their competitive abilities and according to conditions and season. The presence of weeds does not necessarily mean that they are damaging a crop, especially during the early growth stages when both weeds and crops can grow without interference. However, as growth proceeds they each begin to require greater amounts of water and nutrients. Estimates suggest that weed and crop can co-exist harmoniously for around three weeks before competition becomes significant. Weeds can also host pests and diseases that can spread to cultivated crops. Insect pests often do not attack weeds.

Propagation
Seeds
Annual and biennial weeds  propagate themselves by seeding. Many produce huge numbers of seed several times a season, some all year round. Not all of these will germinate at once, but over several seasons, lying dormant in the soil sometimes for years until exposed to light. Poppy seed can survive 80–100 years. There can be many thousands of seeds in a square foot of ground, and soil disturbance will produce a flush of fresh weed seedlings.
Subsurface/surface
The most persistent perennials spread by underground creeping rhizomes that can regrow from a tiny fragment. Their tap roots can put out lateral roots. Other perennials put out runners that spread along the soil surface. As they creep they set down roots, enabling them to colonize bare ground with great rapidity.

Control
Coverings
In domestic gardens, methods of weed control include covering an area of ground with a material that creates a hostile environment for weed growth, known as a weed mat. Several layers of wet newspaper prevent light from reaching plants beneath, which kills them. Daily saturating the newspaper with water helps plant decomposition. After several weeks, all germinating weed seeds are dead. In the case of black plastic, the greenhouse effect kills the plants. Although the black plastic sheet is effective at preventing weeds that it covers, it is difficult to achieve complete coverage. Eradicating persistent perennials may require the sheets to be left in place for at least two seasons. Gravel can serve as an inorganic mulch. Irrigation is sometimes used as a weed control measure such as in the case of paddy fields to kill any plant other than the water-tolerant rice crop.
Manual removal
Weeds are removed manually in large parts of India. Many gardeners still remove weeds by manually pulling them out of the ground, making sure to include the roots that would otherwise allow them to re-sprout. Hoeing off weed leaves and stems as soon as they appear can eventually weaken and kill perennials, although this will require persistence.  Today mechanical devices such a brush cutters are used to remove weeds close to the ground but for sure they will grow back naturally. It is not a permanent method.
Tillage
Ploughing includes tilling of soil, intercultural ploughing and summer ploughing. Ploughing uproots weeds, causing them to die. In summer ploughing is done during deep summers. Summer ploughing also helps in killing pests. Mechanical tilling can remove weeds around crop plants at various points in the growing process.
Thermal
Several thermal methods can control weeds. Flame weeders use a flame several centimeters away from the weeds to give them a sudden and severe heating. The goal of flame weeding is not necessarily burning the plant, but rather causing a lethal wilting by denaturing proteins in the weed. Similarly, hot air weeders can heat up the seeds to the point of destroying them.
Keeping Weeds Out With Mulch
If you followed the above advice, you now have a new bed that contains no perennial weeds, but it does contain weed seed. The best way to stop the seed from germinating is to keep the soil dark. The easiest way to do this is with mulch.
Mulch for a Vegetable Bed
The best mulch for a vegetable bed is straw (some people prefer hay). It can be laid down nice and thick once your vegetable seeds germinate. Or lay it around transplants. It keeps seeds from germinating, holds moisture in the soil and slowly decomposes to add nutrients. You can also use wood chips as described below but you need to be careful that the wood chips don’t get mixed into the soil, or you might have a nitrogen deficiency.
Mulch for an Ornamental Bed
The best mulch for an ornamental bed is wood chips. These are the chips produced by arborists when they take down a tree. Add 3-4″ across the whole bed and you will get almost no weeds germinating. Wood chips slowly decompose as bacteria and fungi go to work. The microbes need nitrogen to do their work and they take it from the soil. This might sound like a problem, and many people think it is, but the microbes only take nitrogen from the top 1/4″ of soil. They do not affect the nitrogen level deeper down where the roots grow and therefore this does not take nitrogen away from the plants.
Cultural methods
Stale seed bed
Another manual technique is the ‘stale seed bed’, which involves cultivating the soil, then leaving it fallow for a week or so. When the initial weeds sprout, the grower lightly hoes them away before planting the desired crop. However, even a freshly cleared bed is susceptible to airborne seed from elsewhere, as well as seed carried by passing animals on their fur, or from imported manure.
Buried drip irrigation
Buried drip irrigation involves burying drip tape in the subsurface near the planting bed, thereby limiting weeds access to water while also allowing crops to obtain moisture. It is most effective during dry periods.
Crop rotation
Rotating crops with ones that kill weeds by choking them out can be a very effective method of weed control. It is a way to avoid the use of herbicides, and to gain the benefits of crop rotation.
Biological methods
A biological weed control regiment can consist of biological control agents, bio herbicides, use of grazing animals, and protection of natural predators. Post-dispersal, weed seed predators, like ground beetles and small vertebrates, can substantially contribute to the weed regulation by removing weed seeds from the soil surface and thus reduce seed bank size.
Animal grazing
Farmers use livestock to control weeds. This has inherent problems as the removal is not permanent and importantly the live stock may chomp off the leaves of the crop.

Chemical methods
Herbicides
Weed control can also be achieved by the use of herbicides. Selective herbicides kill certain targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often based on plant hormones. Herbicides are generally classified as follows:
a. Contact herbicides destroy only plant tissue that contacts the herbicide. Generally, these are the fastest-acting herbicides. They are ineffective on perennial plants that can re-grow from roots or tubers.
b. Systemic herbicides are foliar-applied and move through the plant where they destroy a greater amount of tissue. Glyphosate is currently the most used systemic herbicide.
c. Soil-borne herbicides are applied to the soil and are taken up by the roots of the target plant.
d. Pre-emergent herbicides are applied to the soil and prevent germination or early growth of weed seeds.
In agriculture large scale and systematic procedures are usually required, often by machines, such as large liquid herbicide ‘floater’ sprayers, or aerial application.

Other information
Hybrids
One method of maintaining the effectiveness of individual strategies is to combine them with others that work in complete different ways. Thus seed targeting has been combined with herbicides. In Australia seed management has been effectively combined with trifluralin and clethodim.[6]
Resistance
After all the successes you may have in removing weeds you will encounter resistance as time goes by. Resistance occurs when a target adapts to circumvent a particular control strategy. It affects not only weed control, but antibiotics, insect control and other domains. In agriculture is mostly considered in reference to pesticides, but can defeat other strategies, e.g., when a target species becomes more drought tolerant via selection pressure.

Ways to Make Weeding Easier
1.Weed the day after a rain or after watering – weeds pull out easier in moist soil.
2. Stop a weed from flowering and you stop hundreds of future weeds.
3. Get the root out – if the root stays behind you did not get the weed out.
4. Pull slowly to give the plant a chance to release itself from the soil.
5. Pull the weed out with your hands or a trowel – it is harder work, but more effective.
6. Don’t disturb soil unless you have to.

Information courtesy:
Wikipedia
Robert Pavlis