At the very end of the "Using The Console" section is the below line:
However, this doesn't capture the true power of TAB. It does autocomplete, but it also gives contexual help text when used against each stage of a completed command. If a space is left after a command word it will list the options available.The Tab key will auto-complete commands and player names.
I was trying to write this cleanly and just failed a few times, so thought I'd flag it here and see if a clear & precise explanation just came to anyone else?