What is the difference between an authorization and pre-authorization? And what are their hold times?

A pre-authorization is typically used to reserve funds with a reasonable estimate of how much will be cleared. An authorization is when the amount is known.

Pre-authorizations are used in situations like Automated Fuel Dispensers (AFD), hotel reservations, car rentals, etc.

Authorizations are used to reserve funds for a purchase where the merchant does not capture right away, like buying something on amazon where you authorize the amount of the purchase, then it is captured when it ships.

Pre-authorizations can be captured for up to 30 days according to MC network rules. For Authorization, it can be up to 7 days.

In the absence of any additional messages from the merchant, the hold will automatically be released after 7 or 30 days depending on what type of hold it is.