Degenerate art is a term used by some people a long time ago to describe art that they didn't like. It means art that they thought was bad, ugly, or didn't follow the rules they liked.
In the past, some people in powerful positions didn't like art that was different from what they were used to seeing. They didn't want people to look at or appreciate art that was created outside of their guidelines.
These people wanted art to look a certain way. They didn't like art that was made by artists who were not part of a popular art style or didn't follow the rules that they liked.
They called this "degenerate art" and they said it was bad for society. They didn't want people to see it, and they destroyed some of it.
But many people today think that this was wrong. They believe that all art should be appreciated, no matter what style it is, and that diversity in art is part of what makes it so interesting.
So although "degenerate art" used to be a term of hatred, today it is being reclaimed as a celebration of art that is different, radical, and unique.