What are weeds? How can we control them?

Explanation: 

Weeds are the unwanted plants which grow with the crop and starve the main plant for the nutrients.

Due to lack of nutrition, main crop does not grow properly.

Weeding is performed to get rid off from these weeds.

Weeds can be controlled by spraying weedicides. These are not harmful for the main crop.

Weeds can be removed manually by the means of a Khurpi.

Final Answer:

Weeds are unwanted plants which starve main crop for the nutrients and provide hindrance  in the growth of crop. These can be controlled by using weedicides or removed manually.