In Microsoft Systems Management Server (SMS), an alias for a collection of computers. Machine groups are used to specify the targets and distribution servers for SMS jobs such as Run Command On Workstation and Share Package On Server.
You generally use machine groups when you want to specify exactly the computers for a job, such as when you want to distribute licensed software to clients. Machine groups are used this way because their membership is static. Machine groups contain only the computers that you add to them. This is unlike the Sites window, which contains all the computers that belong to the selected site.