What are weeds how can we control them?

Question: What are weeds how can we control them?

Weeds known as "undesirable plants" which group behind the original crop it is very useless plant because it is feed the nutritions from the original crop and inhibit the growth of original crop so it is very necessary for control them. Some important wedding method such as  "weedicides" it is chemical which used to inhibit growth of weeds. Manual weedicide is "khurpi" and third one is tilling method.