Difference between SPWeb.Users, SPWeb.AllUsers, SPWeb.SiteUsers

MOSS 2007 offers 3 different user collections in the SPWeb object.

• SPWeb.Users
  This represents the collection of users or user objects who have been explicitly assigned permissions in the Web site . This does not return users who have access through a group.
  
  Example (C#):
  SPUserCollection users = web.Users;
• SPWeb.AllUsers
  This gives us the collection of user objects who are either members of the site collection or who have atleast navigated to the site as authenticated members of a domain group in the site.
  
  Example (C#):
  SPUserCollection users = web.AllUsers;
• SPWeb.SiteUsers
  This is the collection of all users that belong to the site collection.
  
  Example (C#):
  SPUserCollection users = web.SiteUsers;

These terms tend to confuse us unless we really know the differences between each one of them.

So I thought it would be nice to write an article stating which is what. Hope this information helps you SharePoint 2007 developers.