The default authentication method for MOSS 2007 is to use NTLM or Kerberos Authentication. This is typically desired for internal intranets/portals to provide an integrated method to authenticate and authorize user to access pages and content. 

When using MOSS to build an Internet or Extranet Site this can be very difficult to use. Managing extranet and internet users through Active Directory is not even practical in some circumstances such as these. Through CodePlex, Microsoft has released a Forms-based authentication and user management solution that address just this issue.

The Official Microsoft SharePoint Team Blog has details on this Community Kit release. You can also go directly to CodePlex to get the Pre-Release Beta of the Form Authentication Community Kit download and code.