Basically, servers run operating systems that are similar to a desktop/laptop, with the addition of applications and features that allow servers to do what they were designed to do ... provide network services (website management, database, directory management, network access/security, email, etc.).  Like desktop operating systems, a license is required to run the OS, and they usually require licenses for all users/devices that might simultaneously access the server - these are your CAL's.

We could go more in depth, depending on what you might want to do with it or want to know.

Ok, so if I'm understanding this correctly, say we have 3 computers that you would need access to the server so we would need 3 CAL's to let all the computers use the server. correct? And this would be for a church, were getting started on the tech. stuff in the church. So i was thinking windows server 2008 standard with the included 5 CAL's.

thanks for the help!

Sounds like you should be ok with the 5 included CAL's.  You can always purchase additional CAL's later.  I'm a little fuzzy as to exactly what types of access require licenses (for example, a web server doesn't require a license for computers accessing the website), but if you have less than 5 computers/users, it shouldn't matter anyway.

Ok thanks, i was a little puzzled by them so thanks for explaining. :emotion-1:

One note about the server operating system. If you decide to create a domain/active directory, you may need to check if the OS on the desktops/laptops can join a domain (e.g. XP, Vista Home Premium, and/or Windows 7 Home Premium cannot join a (Microsoft) domain.