Not a programming question but from the msdn...
Key type Description
CUS This custom key requires special actions to activate or install.
MAK This volume license key (MAK) allows multiple activations.
RTL This retail key allows multiple activations.
STA This setup key bypasses activation.
VL1 This is a VA 1.0 key
OEM This is an Original Equipment Manufacturer key that allows multiple activations.
AAA This retail key is for Academic Alliance programs and allows one activation. These keys are issued in batches.
AAL This lab use key is for Academic Alliance programs and allows multiple activations.
AAM This is a multiple activation key for Academic Alliance program customers.
AV1 This volume license key (VA 1.0) is for Academic Alliance programs and allows multiple installations.