Discrimination is when a person is judging a person of another race with insults, physical abuse, verbal abuse, peer pressure and other things that seem very harmful. For example if a white man call an African American man a bad word then that would be discrimination. Or like how Donald Trump wants to import Mexicans back to Mexico. Another example would be if a group of white children exclude colored people away from their group.
One time I was in Kindergarden and there was mostly white kids in my class. Many of them excluded me and the other Mexican kids from their groups. They said we were very "mean and aggressive". They basically judged us because of our skin color. It was sad. I talked to my teacher about it and the kids didn't seem so happy when I had to play with them. In the end we all got along and we managed to stay friends for some years.