There are many similarities and differences between cats and dogs.
But here are some of the basics:
Dogs are apart of the canine family, while cats are felidae. Canines include, dogs, wolves, coyote, jackals and other kinds of dogs. Felidae consists of cats, leopards, lions, Cheetos and jaguars.
The two animals make different noises, dogs bark and growl.
Cats meow and purr. They both come in different sizes, dogs are typically large/medium while cats are quite small.
Both have four legs and were domesticated by humans. Cats and dogs also benefit us people, cats catch unwanted guests such as mice and dogs can detect objects and beings using their nose.
These are some basic differences and similarities between the two, hope this helps!