OEM, Retail and Volume: how Windows and Office keys differ
Three channels, three sets of rules.
Retail
A full boxed or digital licence. It can move to a new PC.
OEM
Made for PC builders and tied to the first PC.
Volume (MAK and KMS)
Corporate licences. MAK keys have a set number of activations, and KMS needs a company server.
Digital licence
A record at Microsoft: see product key or digital licence.
How to see your type
slmgr /dli shows the channel.
What to choose
Keeping the PC: OEM. Changing PCs: Retail. A home user has no reason to buy Volume.
Does the channel change the features?
No. The same edition has the same features.