A version of windows 10 that is completely free of bloatware (no Microsoft store, no preinstalled apps like candy crush, no tiles on start menu, no Cortana, only windows search, no edge, only Internet explorer). It only gets security updates instead of feature updates, and has support for 10 years. Best version of windows 10 IMO. FYI it was originally called LTSB (Long term servicing branch) and was renamed to LTSC (Long term servicing channel).
I put it on my new machine and it the 1st version of Windows I've been ok with since 7. Buying it is basically impossible for a normal person, but its readily available on tpb. (also kms activator)