FASST is Futaba's term for their method of the many different ways, company's code the 2.4 GHZ RC systems.
As far as I know FASST receivers will only work with Futaba FASST transmitters. I could be wrong as I am a JR man.
All manufactures have their own system with their own name for it.
Some company's like HobbyKing make compatible receivers as well as their own. Of course all of them claim there's is the best.
Because we have several different ways the brands handle switching around the 2.4 band, we as flyers can operate more RC gear in one place without interference than we could ever fly
Here is Futaba's explanation of FASST;