What's The Point Of An Audio Interface?, question Options

[karambos]

Hi,

I have a problem trying to understand what audio interfaces are for. As far as I understand, an audio interface (like something by MOTU or the PROTOOLS 888) sits inbetween the mics you are using to record with and your audio card. Or does it sit between the mics and the desk?

If you are recording a drumkit with, let's say, eight mics, then you could just plug the mics directly into the mixing desk, surely? What's the advantage of having an audio interface to plug your mics into?

THere must be a technical reason but I can't see what it is. Maybe it's just for the convenience of being able to cable any mic to any input on the desk. Is that right?

Please can someone explain why people pay so much for these things?

Thanks