I\'m starting to learn ASP.NET Forms Authentication, and I\'m looking for a good article to help me start.
I\'ve heard before that ASP.NET Forms Authentication uses
The following tutorial from asp.net is worth reading:
http://www.asp.net/security/tutorials/an-overview-of-forms-authentication-vb
Following is the msdn page explaining the Aspnet_regsql.exe command to create the aspnet database.
http://msdn.microsoft.com/en-US/library/ms229862(v=VS.100).aspx
I would like to recommend the msdn articles :
here is the schema used :

aspnet_ tables are part of SQL membership Provider implementation. Forms authentication works on top of Membership Provider.
Here are some articles
You can even roll out your own Membership Provider which uses your existing table.
The Examining ASP.NET's Membership, Roles, and Profile series is a good starting point. It covers all the security part of ASP>NET.