| VST stands for virtual studio technology.
i could go into it but the tl;dr version is that VSTs are effects used in DAWs for recording. Kind of like digital effect pedals, and a VSTi is an instrument based on the same technology--like a synth
if you check out the audiffex site, you can see the VSTs that they sell--looks like a lot of effects designed for guitar and bass. pretty standard stuff. | 
