VST is the format that most DAWs (see below) use for plug-ins. Not all DAWs use VST; Pro Tools uses RTAS format, and some DAWs use AU format. On a Windows PC, you will have a VST folder, usually somewhere within Program Files. A company called Steinberg actually came up with the technology, so it's probably C:\Program Files\Steinberg\VST Plugins\ or something like that. I can't be sure because I'm at work and this PC of course doesn't have those folders. In any case, most DAWs point to that location by default, and have a menu system for adding VST plug-ins to audio tracks. DAW = digital audio workstation, such as Sonar, Cubase, Reaper, etc. A lot of plug-ins also work as stand-alone applications in case your DAW doesn't allow external plug-ins. For example, POD Farm and Amplitube can be run as stand-alone apps "in front of" your DAW. As I mentioned above, some (such as Pro Tools) use a different plug-in format, but some like Propellerhead Record don't use plug-ins other than what is built into the DAW.