If you resort to a course of action that you do not really approve of, you adopt it because you cannot see any other way of achieving what you want.

If you achieve something without resort to a particular course of action, you succeed without carrying out that action. To have resort to a particular course of action means to have to do that action in order to achieve something.

A resort is a place where a lot of people spend their holidays.

If you do something as a last resort, you do it because you can find no other way of getting out of a difficult situation or of solving a problem.

You use in the last resort when stating the most basic or important fact that will still be true in a situation whatever else happens.