Art that isn't clearly a picture or painting of something is called "abstract". Abstract art usually includes shapes, colors, and lines organised in some kind of pattern. It's usually hard to tell what the art is "supposed to be" a picture of. Abstract art first started to become popular in the early 1900's.
The word "abstract" means "not directly connected to real things". So a person's ideas can be abstract as well. Abstract ideas are things like "love", "society", "economics", "evil", and so on. They're not things that can be seen or felt directly.
The opposite of "abstract" is "concrete". Things that can be called "concrete" include:
- concrete objects
- a concrete plan