There is actually no difference at all. A common conversation when discussing receptacles may be referring to a ground fault circuit interrupter (GFCI) as simply a ground fault interrupter (GFI). They are generally the exact same thing.

Is a GFI the same as GFCI?

Ground fault circuit interrupters (GFCI) and ground fault interrupters (GFI) are the exact same device under slightly different names. Though GFCI is more commonly used than GFI, the terms are interchangeable.

Why does my GFCI breaker keep tripping with nothing plugged in?

The reason why its nearly impossible for a circuit breaker to trip without devices being plugged in is because, sometimes, the breaker has simply gone bad and is just malfunctioning. Theres nothing you can do in this case but switch it out for another.