Generally, thet hate each other. It’s not always the case, but if you put a random cat and a random dog together in the same room, it’s not going to work out well. Also…
Dogs want to be your friend. Cats might consider letting you be their friend, sometimes, when they want something.
Dogs might mourn for an owner that have passed. Cats would eat their dead owners.
Dogs may bark and warn their owners of danger. Cats would sleep through any danger.