ASIO is a driver standard developed by Steinberg for low latency audio. An example is probably the easiest way to explain it. Let's say your mixing a song in your mixing software, and you move a fader to increase the level of a track. Using standard DS or MME drivers, it might take up to 1/2 to 3/4 of a second before you hear the results of that fader move. It doesn't sound like much, but it makes it really difficult to make small & fast adjustments. Using ASIO, on the other hand, you might hear the result of your fader move in 50ms! Basically it'll feel like everything is happening in realtime.
Another use for low latency drivers (like ASIO and WDM) is live input processing. Using live input processing, you can apply effects to incoming audio without there being as much of a delay. Consider appling an effect to an incoming guitar signal if it takes 1/2 a second for the effect to happen - you're going to hear a major delay! Now if we can get that down to just a few milliseconds, it's much more doable. Ok, before you get your pants in a knot, you should know that live input processing is difficult and not frequently used, because in order for you not to have any audible delay your latency has to be less than 10ms. This is very hard to achieve as your track count increases.
VST is an audio processing standard also developed by steinberg. It's similiar to DirectX (DX), in that there are VST effects just as there are DX effects. A VST instrument is somewhat similar to an effect, except that it is as it sounds - an instrument. You trigger a VST instrument using MIDI either via a controller or via software. There are VST instruments that sound like pianos, classic synthesizers, etc etc. Note that there are also DX instruments that work in the same manner.
To take advantage of VST instruments you need software that supports VST instruments. To take advantage of ASIO you need both software that uses ASIO, and ASIO drivers for your soundcard.
WDM is a similar technology to ASIO, except that it was created by Microsoft. With modern WDM drivers and software, WDM can do the same things that ASIO can do. DirectX is a similar technology to VST, except that it too was created by Microsoft. I use n-Track which has support for WDM, ASIO, VST, and DX....so it's not like the technologies are mutually exclusive.
Slackmaster 2000
