Many musicians beginning their independent music production have to travel down the path of understanding the signal chain: the equipment that gets your sound from the sound source into a recorded media. One of the main parts of the signal chain is the soundcard (when we talk digital music). It has come to my attention that many bedroom musicians still misunderstand the difference between a soundcard and an interface.
The audio interface
Though most will call it a soundcard (for sake of simplicity), an audio interface (or AI) is actually a pre-amp and converter combined into one body. The purpose of an AI is to raise the level of the incoming sound signal from mic level to line level (this is the pre-amp part of the audio interface), and to turn that analog signal into digital bits (this is the converter part of the audio interface). Many audio interfaces also include +48v phantom power (for use with condenser mics) and are usually connected to the computer via USB of Firewire.
A soundcard, on the other hand, is just a converter. It's called a soundcard because that's what it does in a normal household computer: to convert the digital data in the computer to analog sound that comes out the computer speakers. In normal computers, not many people use the soundcard to input sound into the computer, although it can be used for that also.
A converter that sits outside the computer body is often called an external soundcard. But if you explore the various recording equipment available for purchase, you will understand that a converter doesn't always have to be a card (though it often is). High end premium quality converters are often shaped like a box that a recording engineer fits onto his equipment rack.
By the two explanations above, we can see how a soundcard is different than an audio interface:
1. A soundcard does not have pre-amps. Stand alone converters do one thing: to convert analog to digital data and vice versa.
2. A soundcard is the specialized name for the converter.
3. A soundcard is a converter alone. An audio interface is a converter plus preamps.
I hope this short article can help you better understand the parts of your signal chain.
To your equipment savviness,