Eristic is a big word that means arguing just to win instead of trying to find the truth.
Imagine you and your friend are arguing about which is better, cats or dogs. If you both try to share your reasons and listen to each other's points of view, that's called a discussion. But if you start saying mean things about your friend's point of view or interrupting them so they can't finish their sentences, that's called eristic.
Eristic is like playing a game where the only point is to win, even if you have to cheat or be mean to do it. But just like in any game, it's not very fun for anyone if one person is always trying to win and not playing fair. So it's better to have discussions where everyone can share their ideas and try to come up with the truth together.