Preliminary means something that comes before something else. If you want to run in the race, you have to place in the top third of the preliminary round. It can also mean "early" — the preliminary results are in, and you've won!
Preliminary is often used euphemistically, as in, "There are a few preliminaries we'll need to take care of before you start your new job. First, sign over all your worldly goods to the company, then write a letter to your family explaining that you will never see them again. All set?"