Updated and expanded:
One Night Stand - Self explanatory. Typically free (except for the drinks and/or room). Low risk, but hide your wallet. Emotional connection may occur (see GF).
Street Hooker - Pick up on street corner and do your biz. Minimal engagement beyond the act. No emotional connection and no questions. Low cost, high risk. Emotional connection is possible, but only if you are insane. Hide your wallet.
AMP girl - Will typically service anyone that walks in the door that can pay. Degree of service may depend of the level of connection, however. AMP may bar certain people with bad track records. Typically no emotional connections, but may be open to it. No questions. Low to mid cost. Generally low risk.
Brothel girl - Like an AMP girl, but typically found in Europe.
Motel girl - Similar to AMP girl in some ways, but operates out of a motel for a short period of time (3 days -2 weeks). Typically FS only. Usually no pretense of massage. Emotional connection is possible (especially if she expects to return periodically), but very rare. Slightly lower cost, but much higher risk than a FS AMP girl. Be aware that motels are frequent targets of LE stings.
Legit girl - Girl you meet at legit establishment (massage parlor, nail salon, restaurant). Ply with charm and good tips. Get contact info and start texting. After some period (weeks to months), may transition to SB, Mistress, GF or FWB.
Escort - Will arrange meetings on demand for $$, but may be selective if you creep her out somehow. Typically no emotional connection, but there are exceptions. No questions. Mid to high cost. Generally low risk unless the AMP is under surveillance or is poorly situated.
Sugar Baby - Will arrange meetings on demand for $$, but more exclusive than an escort. You will likely have to audition first before she will see you. Will typically see a small group of approved men. Not as available as an escort. May develop an emotional connection to some men. However, some SBs may function more like escorts. No questions. Mid to high cost. Very low risk, especially if you don't disclose your identity.
Mistress - Heavy emotional connection. Will be exclusive to you. Knows you very well. Understands that you are married and she will always be #2. Financial support may or may not be required. In theory, she is easily disposable, but you may be unpleasantly surprised.
Friend With Benefits (FWB) - Similar to a mistress, but without the heavy emotional connection. Note that an emotional connection may well exist, but is often denied by other parties. Typically no cost. Generally low risk, unless she has a husband or you have a lot of common friends. If an emotional connection develops, may eventually aspire to become a wife. Like a mistress, may or may not be easily disposable.
GF - Mid to heavy emotional connection. Expected to be exclusive (both ways). Knows you well (or thinks she does). Assumes she is #1. Expects affection and tokens there of. Typically, no direct financial support. Provides regular, typically enthusiastic sex, including BBBJs. Aspires to be wife. Can be disposed of with some effort. May also self-dispose on their own.
Wife - Exclusive to you (and expects you to be exclusive to her). Knows you intimately. Assumes she is #1. Heavy financial and emotional support required. May or may not provide sex. If not, see one or more of the above. If she finds out about one of the above, will rip you apart like a wildcat (physically, emotionally, financially).