What is ASP NET Core Identity

In simple words Identity is a mechanism in which 5 to 6 tables are innvolved which are used to store.

User Registeration Information
User Role Information
User Claims & Policies (Permissions)
Role Information

You can't implement Identity direct in Core 2.1 but in 2.2 there is template in New Project area. You can add Identity in ASP.NET Core via Nuget searching Sample Identity.

It will add sample Identity in your existing project.

If you want to use custom properties in you Role or User Table you can create a new class and inherit that from IdentityRole and IdentityUser respectively.

Conclution:

Quick starter user management by .NET is Idetity.