This is where your inbox is stored and where any folders you create are stored. News Stand is used to point at a Usenet News server, if you want to use Simeon for reading Usenet News. Local is for messages that will be stored on your local computer. These are not accessible from other machines. Folders - are separate files of messages that you create to archive your messages.
Folder names are case-sensitive and can include spaces so they can be very descriptive.
One company representative told me he had 120 different folders, for different projects he was working on. These folders can be subscribed or unsubscribed so that only some are visible at any one time. The inbox is one folder that is automatically created. Message Groups - are separately labeled areas that you can create within folders. This is a way to organize the messages within a particular folder by filtering messages depending on the sender, subject or some other criteria.