Essentially they are the same thing. Put simply, if your cat has a pedigree, it is a purebred. If it doesn’t have a pedigree your cat doesn’t belong to a breed.
But, cats are not dogs (no matter how similar Siberians are to dogs in behavior!). Cats weren’t domesticated like dogs as humans barely intervened in cat breeding until very recently, around 150 years ago with the majority since the 1960’s (unlike dogs 20,000 to 40,000 years ago). Therefore, cats with a pedigree are a minority, as only around 1-3% of cats belong to a breed. So all pedigree cats have all domestic ancestors. The breeds are so recent that with the pedigrees you can often actually trace back to the foundation cats of the breed!
However, there are no true and reliable breed tests available for cats. Those which advertise cat DNA tests, aren’t actually testing for breeds. They don’t tell you what is the breed or “breed mix” of your cat, but instead they tell you what is the DNA similarity to some of the cat breeds. At best they are highly unreliable.
All of our kittens and adults are Pedigreed (& therefore purebred) from award-winning ancestors ensuring the highest of breed qualities including low FelD1 levels in our kittens.