GFE = intimacy. Kissing, LFK, DFK, cuddling, etc.
PSE = cumming on a girl's face, fucking her in any/all positions, "treat me like a slut", etc. I'd say pretty much anything you see in a porno, but porno's gotten really fucked up lately and even I wouldn't expect a PSE SP to provide fisting, DP, 3P, ass-to-mouth, etc.
The problem with PSE is that FAR too many girls think they know what it means but really don't have a clue. You've gotta be pretty liberal to provide a PSE.