SharePoint Server 2010 capacity management: Software boundaries and limits

http://technet.microsoft.com/en-us/library/cc262787.aspx

This article describes software boundaries and limits of Microsoft SharePoint Server 2010. These include the following:

• Boundaries: Static limits that cannot be exceeded by design
  
  
• Thresholds: Configurable limits that can be exceeded to accommodate specific requirements
  
  
• Supported limits: Configurable limits that have been set by default to a tested value