3 4 Edge Overload X - The X just means he can be anything (algebra) - QB Spy, blitz the middle, HB spy, double a receiver...anything. The swiggly lines simply mean man coverage. The DE's rush the outside half of the tackle and the OLB's follow, forcing the gaurds and tackles to figure out what's going on. That leaves the middle open for the offense, but also for the defense, as the DT is probably one-on-one against the C and the MLB has a free shot at the backfield.