Question : KMS and MAK

Hello,
we have a small network.
But I have seen we have some different license keys.
Can you explain to me, what is MAK and KMS ?

On site : EOPEN, I can see 3 different types of Licenses:

1. Volume License Key NA
2. Volume License Key KMS
3. Volume License Key MAK 0/15

Can anybody explain this in detail and easy to follow ?

Answer : KMS and MAK

MAK key is a Multi Activation Key and you have 15 activations using that key of which you have not used any yet.
KMS is for Key management Server and allows you to activate licenses within your own network.

See here: http://www.microsoft.com/licensing/existing-customers/product-activation.aspx