User Authentication
Many web applications usually require user signup. The objectives of having users sign up vary from providing member-only content to customizing services based on the users' data.
When a user signs up for a web application service, the web application registers the user's essential information, including user name, email address, and password (user identity).
When the user logs in to the service, the web application checks if the user is the same person who has previously signed up for the service. The process of verifying the identity of the user is called user authentication.