Art criticism is like looking at the pictures in a book and telling people what you like or don't like about them. Just like when you draw a picture and your parents tell you how good it is or what things you could improve on, art critics look at paintings, sculptures, and other art and give their opinions on them.
When someone is doing art criticism, they might talk about things like the colors used in the artwork, what the picture looks like, if the shapes in it are interesting or not, how good the drawing or painting is, and whether or not the artwork makes them feel a certain way.
Sometimes people might not agree with what an art critic says, and that's okay. It's important to remember that everyone has different tastes and opinions when it comes to art. Just like how you might like to draw pictures of animals or superheroes, other people might like to look at abstract paintings or sculptures.
Overall, art criticism is just a fancy way of talking about art and sharing your thoughts and feelings about it with others.