The INCLUDE keyword allows access to a license, while the RESERVE keyword guarantees access. For instance, say you have 25 concurrent LabVIEW licenses and 40 users that you want to have access to these licenses. You could use the USER_GROUP keyword to create a group that contains these 40 users. Then, you could use the INCLUDE keyword to grant them access to these LabVIEW licenses. Then these users would be able to check-out these licenses on a first-come first-serve basis.
However, say you have five key developers who you want to have guaranteed access to these licenses. You could use the RESERVE keyword to guarantee these five users access. The other 35 users not given reserved privileges would then share access to the remaining 20 licenses on a first-come, first-served basis.
If you have purchased a non-concurrent license for a product, you can only grant access to as many users or hosts as you have seats for. If you try to grant permissions for more users or hosts than there are seats, you will receive a licensing error.