The Devise gem is an authentication solution for Ruby on Rails applications; it helps you set up production-ready user authentication in your projects without having to do everything on your own. Devise provides many useful features such as handling user sessions and adding support for third-party sign-in with OAuth using the OmniAuth gem. Devise also comes with built-in modules for functionalities like resetting forgotten passwords, tracking sign-in count and timestamps, defining timeouts, locking accounts, and so on..
