What is the difference between a plant and a weed?
Weed is a term used to refer to any plant that is growing in a place where it is undesirable or where it might be a nuisance. The term is often used to describe invasive or unwanted plants.

A plant is a general term used to refer to any living organism that is capable of producing its own food through photosynthesis. This includes weeds as well.

The main difference between a weed and a plant is one of perception and context, rather than a scientific distinction.