Queues in MS CRM

There are a lot of misconceptions about queues. They only apply to cases and activities.  While the terminology is the same, assigning a case or activity to a queue is not the same as assigning an entity to a CRM user or team. Programmatically what is being used is a RouteRequest rather than anAssignRequest.

To get a better idea how this works we'll look at database. There are two entities storing queue information, the Queue and the QueueItem. These are not customizable.

Queue – (table) contains all queues

• There are two queues automatically created for each CRM user. 
  • Assigned
  • In Progress 
• Any user defined queues that you create are also stored here.
  • example:  My New Public Queue

QueueItem – (link table)  Contains an entry for each entity assigned to a queue.

• An item can only belong to one Queue at a time,
• The only entities that can below to a Queue are:
• Activities ( email, tasks, etc. )
• Cases

reference : 

http://crmscape.blogspot.com/2008_11_01_archive.html