College rivalry is when two colleges, or sometimes more, have a strong dislike for each other. It's kind of like when you and your friends want to beat the other team in a game, but on a much bigger scale. People who go to one college often have a lot of pride in that college, and they think it's the best one around. They may make fun of people who go to the other college, or try to prove that their college is better.
Sometimes, the rivalries can get pretty intense. People might paint their faces or wear crazy costumes to show how much they love their college. They might shout chants, or even do a well-practiced dance routine before a big game. Sometimes there are even pranks between the colleges, like when one group covers the other college's statue in the rival college's colors.
College rivalry is all about having fun and showing your school spirit, but it's important to remember that being friendly and respectful is also important. The rivalry should stay on the field or court and shouldn't turn into anything mean or hurtful.