Since the introduction of Active Directory, Microsoft added new classes and attributes to the schema with each Windows Release which addedd more and more functionality to the AD. Here is the version table just to understand the versioning.
| Windows Server version | Schema version |
| Windows 2000 Server | 13 |
| Windows Server 2003 | 30 |
| Windows Server 2003 R2 | 31 |
| Windows Server 2008 | 44 |
| Windows Server 2008 R2 | 47 |
| Windows Server 2012 | 56 |
| Windows Server 2012 R2 | 69 |
Use the Get-ADObject cmdlet in the Windows PowerShell to get the version of the schema of your AD.
PS C:\> Get-ADObject (Get-ADRootDSE).schemaNamingContext -Properties objectversion
Download the following file for you to understand more of “Combined Active Directory Schema Classes and Attributes for Windows Server”
Follow Link: http://www.microsoft.com/en-us/download/details.aspx?id=23782
Schema Version Attribute: http://msdn.microsoft.com/en-us/library/ms679651%28v=vs.85%29.aspx