Ummmm, could you help me please?

Ummm ok, so the most random thing in the world just happened to me. I was on the internet just screwing around and all of a sudden this weird thing pop's up. "You are at risk for (I forget the virus name)" And then some other window pops up and a scan starts running, so I figured, "Uhhhh ok I guess it's just getting rid of viruses or something?" And then it says viruses detected 3, but was able to get rid of one cause it wasn't a huge threat. But the other two it said were high threats. One was a advertiser and I don't remember what the other one was. Is this like just a stupid scam or ad or something because I have no clue what the heck it could be. I clicked off of it and it said "Do not click off unless you want your computer to be (I forget the word but it was something slang and weird) so I figured if it was real it wouldn't say something stupid like that and it would say something that made a little more sense. I just have no clue as to what the heck this is. Could you please help me? Thanksss! =)