The zmmboxmove command has a -sync option....and I always use it.....but I don't know why.

The online documentation is pretty thin. The CLI help just says...

-sync,--sync         Run synchronously
OK synchronously with what? It runs synchronously with other zmmboxmove actions? It runs synchronously and allows the user to stay logged in? It runs synchronously with the 6 o'clock train to Waxamahatchee?

Can someone shed some light on that. I'm curious if I do or don't need to use that option and what affect it has on the mailbox or server.