The ASP.NET Core Identity is a membership system, which allows us to add authentication and authorization functionality to our Application. A user can create his/her own account with it and access the system, which is based on his/her roles or claims. It can configure with SQL Server database. It also provides the features to authenticate a user, which is based on his/her external login providers such as Facebook Google, Twitter etc.
You can learn to authorize a .NET Core Identity user with role from these links.