Audio interfaces are devices that connect to a computer (PC or MAC) to provide additional audio inputs and outputs, via a single USB cable. Think of an audio interface is a external sound card for your computer, enabling you to bypass the cheap inbuilt sound cards when recording audio on your computer. An audio interface also performs the critical analog to digital (A/D) conversion.
Great for home recording!
A small USB audio interface can be one of the best and least expensive ways to started with home recording. Often with dual inputs microphones and/or instruments, enabling song writers to record vocals and guitar simultaneously to separate audio tracks, enabling individual track mixing and mastering within the recording software for really professional results.
Most audio interfaces will come with FREE recording software. For example, the "M-Audio Fast Track USB" device comes with Pro Tools, the most famous audio production tools in the world. Purchasing this device is one of the cheapest ways to actually get the software, and you get a device!
Outputs for Headphone Playback - while Recording
One of best feature of these units is that they can allow you playback audio from your computer to your headphones, while you are recording. Think you have just recorded an acoustic guitar part, and you now need to hear the guitar played back on headphones while you are recording the vocal track.
Phantom Power PROVIDED!
That's right, all audio interfaces with XLR mic inputs will supply phantom power. Meaning all studio condenser microphones are instantly compatible.