What is the difference of a soundcard and a audio interface?

Mason C Asked: What is the difference of a soundcard and a audio interface?

I am starting a home studio and I have been told I need a soundcard because the one in my computer isn't good enough then I have also been told that I need an audio interface. I just wanted to know the difference here is the audio interface I bought.

http://www.amazon.com/M-Audio-MobilePre-Mobile-Preamp-Interface/dp/B0000TP57E/ref=wl_it_dp_o_npd?ie=UTF8&coliid=I3EONVJ3YKU7L9&colid=RVME3SQ9CGX8

It is a pre-amp and audio interface. Do I still need to buy a separate sound card?

Thanks for the help and I also don't know what cables to buy. Help with that too.