How do I register an application?

When I click on the link to register an application it sends me to a page that has three options...Am I supposed to know what one to pick ? Am I in the right place?

Adaptive Payments

The Adaptive Payments API allows merchants and developers to pay almost anyone and set up automated payments.

Express Checkout
Express Checkout allows merchants and developers to minimize the number of steps customers must complete when they checkout.

PayPal Payments Advanced
PayPal Payments Advanced allows merchants to enable their online stores to collect payment directly via credit card or via PayPal Express Checkout.