Ad url redirects to multiple urls!

Hi, sorry for asking a newbie question but I've seen a lot of popups, cpc, cpm ads redirect to multiple urls before finally reaching the landing page! What do these guys use?

If I am an advertiser is it okay to use redirected urls? I thought networks like Google/Bing bans these kinda ads that represent different urls other than their destination page.

What am I missing?

Need advise plz!