There are many ways to authenticate users in your application. Often, sites require a username and password, but others allow you to login with another account, such as Facebook or Google. Sometimes websites include two-factor authentication, such as with an extra application like Duo or a physical device like a YubiKey.
This tutorial covers the basics of authenticating with usernames and passwords. We'll do this by building a complete web application for submitting help tickets. The front end is built with the Vue CLI and the back end with Node, Express, and MongoDB. This will give you a solid foundation that you could then expand on later.