Yes, both of them format data using the same formatting rules. sprintf() returns the formatted data as a string, which the user can store or further manipulate or display as appropriate. fprintf() writes the formatted data to whichever file or device (such as a serial port) it is connected to.
You may have also seen reference to fwrite(). fprintf(fid,...) is (for these purposes) the same as fwrite(fid,sprintf(...)) but fprintf() does not (theoretically) need to build the entire string before writing it out to the connected device. fprintf() could be thought of as a convenience for the combination of sprintf and fwrite, but it is a convenience that is used often enough to be worth having.
(There is a small difference between fprintf() and sprintf() if the destination is a serial port, but it is unimportant at the moment.)