[dsmithatx]

FTP TCP and IP are protocols, GSM is a european standard and REST is an easy method for building applications in which the backend is called the API (application programming interface) which typically use the http protocol. RESTful generally means using CRUD create, read, update and delete although it isn't a standard.

Some api's are private as in the one your bank's mobile app most likely uses. Some companies offer their API's to the public. They are both still APIs though.