people used to talk just about soundcards, but now that many soundcards come with elaborate input/output schemes, we talk about interfaces too. an interface is just where you plug in your audio sources and midi devices to be recorded , plus headphones, stereo, mackie powered monitors or whatever, to listen to what you are doing. the interface for a typical soundblaster is on the pci card itself, namely, the mini jacks and game/midi port. the interface for a Delta 1010 is a box that attaches to the pci card via a proprietary cable (a 'breakout' box). there are a lot of prosumer soundcards out there, with different types of interface...e.g., some offer mutiple channel inputs, while others have midi, or preamps, or whatever...these days the interface is a big part of making a soundcard decision....