Dynamics Navision Full User and Limited User Structure

• Full User 
  
  Full User licenses provide users full read and full write capabilities to all of the licensed solution functionality through any and all modes of access, including the Microsoft Dynamics NAV Windows client, the Microsoft Dynamics NAV Web client, or any other mode of access including web services. Full User licenses are for users requiring unlimited read and write access. As long as the number of users needing simultaneous access to the solution does not exceed the number of Full User licenses you have acquired, these users are properly licensed for full read and write access to the complete solution functionality.
• Limited User 
  
  Limited User licenses provide users full read, but limited write, capabilities to all of the licensed solution functionality through any and all modes of access including the Microsoft Dynamics NAV Windows client. The Limited User license is designed to give customers a lower-cost alternative for extending ERP to users who only require limited access to the Microsoft Dynamics NAV application:
• Read access to data contained in the solution through any client accessing the application, including but not limited to the Microsoft Dynamics NAV Windows client, the Microsoft Dynamics NAV Web client, and web services.
• Write access to a maximum of three application tables in the object range 0 – 99,999,999 other than the General Ledger Entry table, through any client accessing the application. Access to the General Ledger Entry Table requires a Full User license.
• Device Only User 
  
  Device-only licenses enable a user to connect, provided there is an enabled device available to use. Devices can be full or limited. Device users have either full or limited access, as determined by the device.
• Windows Group 
  
  Use this license type to create a Microsoft Dynamics NAV user based on a Windows group. All members of the group inherit permissions for the user.
  
  Windows Group licensing is a form of license multiplexing. Multiplexing does not reduce the number of user licenses required to access a Microsoft Dynamics NAV solution.
• External User 
  
  This license type is specific to individual users of Microsoft Dynamics NAV 2013 R2. External user licenses must not be shared with other individual users. You do not need concurrent user CALs for external users. External users must not use any clients provided by the Microsoft Dynamics NAV 2013 R2 Application Programming Interface (API), such as the Microsoft Dynamics NAV Windows client or the Microsoft Dynamics NAV Web client. External user licenses must not be used for business process outsourcing purposes.

Source : http://msdn.microsoft.com/en-us/library/jj551750(v=nav.71).aspx