Yes, you understand correctly. You setup a page/post on your site where the content is locked for the visitor and he/she must take an action to unlock it. That action can be filling up a survey, submitting their email address, their zip code - CPA offers, liking the page, etc.
You can get the locker and the locker and offers from the CPA networks you are a member of. If you're not, there is plenty of info here on how to become one, which ones are good, etc. Start with the CPA Section of the Money Making subforum and read all the Sticky posts there.
There are many people that have written in threads about using content locking and their experience with it. Search around and you'll get some very valuable info.