A "F" What? A Savannah cat is a cross between an African Serval and a domestic cat bread to make a F1 Savannah. That is where it all starts! This is a Wild Cat or Hybrid Cat or even Ferrel Cat breed, which is why they are so regulated and require proper consideration before purchasing one.
F1: Savannahs can be as high as 75% Serval or Wild. They require licenses in many states and are literally illegal in some. They will get along or tolerate other pets and usually gravitate to one person. They do not like to be held but love to be petted and are friendly, playful and active in nature. They will grow between 15-30 pounds.
F2: Savannahs can be as high as 50% Serval Wild. They too require licenses in some states and are illegal in others. They get along well with other pets and bond with several people including small children. They will let you hold them for short periods of time, but prefer petting and playing attention. They will grow between 15-25 pounds. They are extremely doglike in their behavior. They will follow you around and walk on a leash!
F3: Savannahs can be as high as 12.5% Serval or Wild. The best of both worlds, a unique wildness for fun but tame enough to be a great domestic pet. They will let you hold them a bit longer, and love attention and are more friendly than just tolerant to other pets like the earlier generations. They are very good with children and make a better choice for a busy family environment.
F4: Savannahs are closer yet to a domestic cat and other than their wild playful nature and dog behavior they are on the same consideration level as many pure bread breeds like Siamese. Some temperament traits but very domesticated.
"SV, xSV, B, C, SBT" These are distinctions generally associated with the male or Stud Savannah cat because most Savannah males will not be fertile to reproduce until they are generation F4 or higher. Therefore, it is not generally a consideration for choosing a Savannah cat as a pet.
Warning: SAVANNAHS are little rascals.