A white cat could be one of many breeds of cat, but it is likely it is a Domestic Shorthair or Domestic Longhair. These are cats with very mixed genes and no particular breed.
Domestic Shorthair or Domestic Longhaired cats can vary in terms of body shape and size. However, if the cat is indeed fat (you cannot feel its ribs under fur, and has no waist), it is likely being overfed or being fed the wrong sort of food.
The Maine Coon is the largest breed of domestic cat.
Tom from Tom & Jerry is a blue and white domestic shorthair.
No cat breed as I know if is restricted to only that colour pattern. It can occur in many breeds, mot notably the domestic. A domestic is a no breed cat but different countries domestics can look different. An American Domestic shorthair can be more leaner and slender than the British Domestic shorthair. I owned a black cat with a white face (how you described) but she also had white paws and a white chest. They look similar to cats in tuxedo's.
A white cat can be of any breed. It is simply a white cat.
The NoNoNo cat is a Domestic Siberian Cat
You can't tell the breed by looking at the colour of a cat. It could be a range of breeds, or most likely a mixed-breed.
It is not a breed, it is simply a coat pattern, called "Red Tabby & White". It occurs in many breeds as well as in non-pedigreed domestic cats.
The black and white pattern on Felix that you are referring to is usually termed "tuxedo", and Im guessing that he was just your everyday domestic short-haired cat
the breed was probably just a domestic ... she was just a basic black witch's cat.
A Maine Coon Cat is a very large breed of domestic cat.
A York Chocolate Cat is an American breed of longhaired domestic cat.
American ShorthairCorrection:Actually, there is an actual breed of cat called American Shorthair. It resembles the British Shorthair cat breed, but less stocky in build. The correct term for a mixed breed is "Domestic Shorthair/Domestic Longhair", often called "Moggy".