gpupdate – What does /force do anyway?

It FORCEs reapplying all policies. It wasn’t a great name choice.

What does /force do anyway?
gupdate /force reapplies all policies
gupdate only applies new policies

What force doesn’t do is force the GPO if it needs to reboot or logoff.
/boot or /logoff will force a reboot or logoff after applying group policy if it’s required.

Here’s the other options while you’re here.

/wait:<value> waits the value (-1 to 600) in seconds for gpupdate before returning to the prompt. The policy continues to process in the background after the time limit.
-1: wait forever
 0: do not wait (useful for scripts)

/target:<target> only applies the target (computer or user) policy

I don’t know what the hell /sync does.