What exactly does that mean..I've heard a couple different things about it can somebody fill me in

 

it means all the inner parts or your engine are from the factory. Stock pistons, rings, crank shaft, connecting rods...

 

Ok which mean that the person has heads and intake done to the car?

 

no.

internals like stated are in the block has nothing to do with the top end wether it be stock heads/intake or aftermarket.

 

Thanks man I was a little lost on that cause I know a few people that say that and they're cars are pretty fast

 

"internals" typically refers to crank, rods and pistons. There's more to it than that, but that's the easy way to think of it. Upgraded internals like forged rods and pistons for example are more a durability modification than a power increasing mod. You can get more power with more compression and all that but typically when you upgrade the internals its to increase the durability of the engine under high horsepower applications.

A heads and intake upgrade (often done with an upgraded cam too and referred to as H/C/I [heads/cam/intake] upgrade) involves replacing the heads and intake manifold and camshaft of the engine. The upgraded heads and intake flow better than the factory parts and the upgraded cam takes advantage of the better flow and the result is more power! It's a really popular swap on older V8s like the 5.0 and chevy ls motors...