Record sound from the computer itself?

Is there an application I can use for mac that can record sound internally, not with a microphone? I wish for this to be possible for the same reason I wouldn't take a photograph of my screen to take a screenshot. So, no external sounds, just record the output?

Try Audio Hijack Pro

Why thank you.

Also, this is the first time my existence has been acknowledged here

I use WireTap Pro for the same thing. It was part of one of the Mac Heist bundles and it works really really well.