The 1.x versions of the product defined the scope of control of the management server (the site) in terms of the NT domain being managed.
Since the 2.x versions, that site paradigm has switched to a group of subnets that will be managed together.
Since SMS, 2003, the site could also be defined as one or more Active Directory sites.
The most frequently used feature is inventory management, which provides both hardware and software inventory across a business enterprise.
The major difference between the 2.x product and SMS 2003 is the introduction of the Advanced Client. The Advanced Client communicates with a more scalable management infrastructure, namely the Management Point. A Management Point (MP) can manage up to 25000 Advanced Clients.
Microsoft introduced the Advanced Client to provide a solution to the problem where a managed laptop might connect to a corporate network from multiple locations and thus should not always download content from the same place within the enterprise (though it should always receive policy from its own site). When an Advanced Client is within another location (SMS Site), it may use a local distribution point to download or run a program which can conserve bandwidth across a WAN.
Microsoft released the current[update] generation of the product, System Center 2012 Configuration Manager, in March 2012.