What's the difference between authorization and authentication?

Authentication is the process of verifying a user. On the other hand, authorization is a process of giving someone the ability to access a resource.

Why are we using firebase? What other options do you have to implement authentication?

We are using firebase for authentication and hosting purpose. Other alternative to firebase auth are: okta, auth0, stytch, oneLogin, Amazon Cognito.

What other services does firebase provide other than authentication?

Beside authentication, firebase provide cloud hosting, cloud functions, cloud storage, cloud messaging, google analytics, remote config.