It's just there to on your profile that you got the medal of completing specific tasks on what game you were playing getting you a achievement of what you were doing. Each medal has a point value of 5, 10, 25, and the 100 points. 5 being the easiest and 100 harder that depends on what type of game you were playing on Newgrounds.
It's similar to the Xbox 360 with the Gamerscore that you get while you play the game. It's pointless I must agreed, but others just do it to for bragging rights with the most medals. I do play games on Newgrounds if I want to.