It's something called Spokeo.
Look it up.
plus there are a vast amount of various methods too.
No offense meant but I don't really trust those service. Just to let you know why, I tried to lookup for a friend whom I've never spoke with for a long time. I tried searching in google for free people search engines just to try my luck. Just like spokeo, i came across
this service and told me it was free. I found 2 matches with same location and tried calling those. Unfortunately,I wasn't lucky enough. So I thought, it's really not that accurate. I tried calling 411 instead.
Well it's just one of those service that if it's free, you will not get the best quality. Just a thought, are there other ways to lookup numbers online? I don't mind if it will cost me.