this is an external sound card, complete with everything you might need: a mic preamp and instrument/line inputs.
it comes with 24 bit/48 Khz converters, a much higher resolution, dynamic range and frequency response than a common onboard card.
i hope it helps to clear things out.
If you are to consider an external soundcard, please look into professional brands, like M-Audio, MOTU, Apogee, RME etc...
they cost a bit more, but give greater satisfaction in the long run.
Do NOT be fooled by Creative Soundblaster's products: these are gamer cards, they will drive you mad with latency problems (like audigy).