AUDIO INTERFACES

What does an audio interface do?

Basically an audio interface connects an audio source ( mic/guitar/DJ Mixer) to a Computer where you might be Recording or Managing sound to Speakers. An audio interface upgrades the sound output of a computer.  Most computer sound cards and outputs are not intended for higher resolution output associated with music recording/production and DJ production. An audio interface prepares sound that you input into your computer.   Assists you to record with a higher quality sound resolution.

Inputs and Outputs

Ask yourself?   Do I need more inputs to allow for e.g.  Vocal and Guitar input at once.

The mix can be input separately into a computer so editing levels independently on your recording program is possible.

Recording multiple musicians simultaneously  on separate inputs.

Multiple outputs to multiple sources... for e.g.. you performing a live set whilst recording into a device, you'll need separate outputs.

Separate speaker control for master speakers and monitor speakers.

DJ's gain a separate output for headphone mixing.

Midi_Interface    

If you need to input from older retro music equipment via the MIDI -output. 

USB Audio Interfaces are popular, offering a very common connection which is fast.