Hey im new too the tuner scene but i was wondering what does it mean to have a built motor??? Like do they just open up the motor and put in new internals or what?  

Generally when someone says they have a "built" motor, they have gone thru it and replaced most, if not all, of the stock internals. such as crank, connecting rods, pistons, camshaft, valves, rocker arms, etc etc.