Question about pop-ups

I'm new to the forums, and this might seem a noob question, but I've seen many big sites (the pirate bay, subtitle seeker) use the "pop-up method", showing a "win an iphone" or advertising an online poker platform in a new web browser window.
I was really curious how is this called (some IM jargon?) and how profitable it is (conversions are probably horrible, considering people are so used to these pop-ups).

I have heard of pretty good conversion rates, if you have the niche.

Well the ads seem pretty general and unrelated to the niche.