Hold on: to wait
E.g. Hold on until mom is here.

Hold off: to postpone, cancel, or stop an action
E.g. He held off preparation for the business trip.

Just to confuse you more…

Hold off on:
E.g. She decided to hold off on her vacation plan.

Hold off from:
E.g. He held off from entering the house.

Ref:
http://www.differencebetween.net/language/difference-between-hold-on-or-hold-off/
https://www.merriam-webster.com/dictionary/hold%20off%20on