Loopback and Audio Hijack from Rogue Amoeba can seem like very similar products. In this video I'm talking about the core difference between the two applications and demonstrate this on the Mac.

If you're after a simple answer and don't want to watch the video...

Audio Hijack is all about rerouting, mixing, processing and recording or streaming audio from multiple sources that already exist on your computer.
Loopback creates virtual audio interfaces which can then be used in other software, including Audio Hijack.

There we go, that wasn't too hard. Please consider watching the video to see a demonstration of both pieces of software in action.

I am a huge fan of Rogue Amoeba software. It's beautifully designed, has a fantastic user interface and works reliably whilst, above all, being incredibly useful. If you do anything audio related on a Mac, these two pieces of software are worth having in your arsenal.

NOTE: I purchased the software myself. This is not an advert.