There are two types of machines, each having a specific business scenario:
Standard Machine - should be used when the name of the machine on which you want to define Robots remains the same each time you connect to it - the standard scenario. You define the machine once, and then can connect to any number of Robots in the Robots page. A Robot in this scenario connects to Orchestrator using the machine name - machine key - username combination.
Machine Template - should be used when the name of the machine on which you want to define Robots changes every time, as in the case of non-persistent Virtual Desktop Infrastructures (VDI). You define this entity once and then connect to any number of Attended Floating Robots using a unique Active Directory username. A Robot in this scenario connects to Orchestrator only using the machine key and username combination.