Cats fight for several reasons, including territorial disputes, competition for resources, or simply because they have different personalities. In multi-cat households, conflicts can arise if one cat feels threatened or if they haven't been properly introduced. To reduce fighting, make sure each cat has their own space, food bowls, and litter boxes. Gradual introductions and positive reinforcement, like treats when they're calm around each other, can also help. If the fights are severe, consulting a vet or a cat behaviorist might be necessary.