While there is no “set” definition, this is generally what they mean and how I use them.
GFE stands for Girlfriend Experience.
With GFE you can expect conversation, kissing, and cuddling. GFE is a great option for first time bookers.
A condom is always required for GFE.
Some of the things that are provided with GFE:
Kissing, CS, BJ, CBJ, COB, BBBJ, DATY, HJ ***

PSE stands for Pornstar Experience. This service is usually a little more naughty.
Just like on a porn set, no condoms are used, which is why PSE requires getting bloodwork done.
Some of the things that are provided with PSE:
Kissing, Raw, 69, BBS, BJ, BLS, CBJ, CIM, COB, COF, BBBJ, BBFS, DATY, HJ, MSOG, OWO, Toy Show (upon request) ***
***Don’t understand what an abbreviation means? Try looking here!