If you are building a website that requires login, and you wish to allow users to securely login with username and password, a google account, facebook account, etc. then you can use firebase authentication!
First, you will need to login to Firebase, click the console button on the top right corner, create a new project as instructed, under build, click on authentication. Then, follow the instruction in the source linked under the external resources section below which will help you in setting up authentication for users in firebase.
Below is a tutorial in learning the firebase authentication on websites. You can perform authentication of the users using Email and Password, Facebook, google, and much more. See the website tutorial for more details.