Clowder is the most common name for a group of cats.
When you see a group of cats the most common name and what the group of cats are called a Clowder.
Another name for a group of cats other than Clowder is glaring.
When cats are in a group and are uncertain of each other they are usually referred to as a glaring of cats.
When the cats are kittens the group of kittens are commonly called a kindle of kittens.
So you can call the group of cats a clowder of cats or glaring or when they are kittens you can call the group of cats a kindle of cats.