How do popular apps authenticate user requests from their mobile app to their server?

Question

Say I have an Android application that connects to a .Net API for receiving/setting data. The confusion that I have is regarding how to sign-up/login the user first time and

Answer 1

I am newbie but I will try to give logical solution for the given question.

There will be two options, [1] For every URI, http authentication will be perform where user's entered credentials will be verified and user shall access resources.

[2] Another approach could be, a user shall authenticated and on every authentication a unique token will be generated. Using generated token, user shall access resources.

Though I'm not sure which approach could be best suitable for mobile application.