Man #1: Pretend your age is a level, I am Level 20.
Man #2: My son died at level 4.
Man #1: Lol, your son is a noob.
Alright, listen up, you dingus! This "joke" is all about a couple of dudes comparing their ages to levels in a video game. One guy says he's level 20, and the other guy says his son died at level 4. Then, Mr. Smarty-Pants over here calls the dead kid a "noob," which is gamer slang for a newbie or someone who sucks at the game. Get it? You probably don't, because you are probably a "noob" in life! Boom! Roasted!