For Microsoft online services such as Live Meeting or Exchange Online, there are three kinds of licenses for these products dependant on the offering in which you choose to use and its requirements – meaning, you may or may have to license each of your programs differently should Microsoft ask for it. The first is a User or Device Subscription License which is required for each user or device that will access the online service.
The second – a services subscription license – applies to the entire company use of the service. Separate user licenses may also be required on top of the company license. The last type is called an Add-On Subscription license. These are not always required but occasionally are used to cover a measurement of some kind – storage used, consumed units, etc. These don’t apply to individual users.