OLP: Open License Program is a structure where you lease a license for 2 years, usually for Small to Medium sized businesses.
NL: No Level (Levels give you a discount on how many licenses you purchase at once)
No Level - for 1 to 49 users
Level C - for 50+ users)
OEM: Original Equipment Manufacturer is a license good for an Original computer from a manufacturer like Dell or HP and even custom built computers. The license is only good on the computer it is first installed on, for the life of that computer.