what is congratulation ads mean? "congratulation you have won"

Please for give me if this not the right place, but I have question. what is the "congratulation you have won" mean. it is USA ad but then it annoys me. are they virus or spyware or just harmless pop-ups. Please give me an answer for this ad??????

 

there are heaps of these adds. most of the time they're just popups and sometimes spyware. they are rarely virus's, just ad's placed to make you buy something.