Newbie To Vst Software: Simple Questions, Are all VST's "post" effects? Options

[Mixolidean]

Hello,

I am a Music teacher that finds himself solving mac problems for other teachers at school. So, now I have some hopefully simple questions: VST Related.

I see these VST apps in magazines, are they mostly Post Audio import effects? I run DECK BIAS 3.5 on a 600 MHZ 768 RAM G3 Graphite iMac. Deck says it's VST compatible and I have tried downloading some Free VST's, but can't get them to appear in the pluggins.

One last question please: if VST's can be operated on incoming signals, is there a VST that will act as a compressor limiter. I have a Roland compressor for Vocals, but I don't want to have to change the settings for the Keys, Guitar, bass .......etc. If there is such a VST, I imagine it would be processor intensive.

Thanks for your time. Oh, what what does VST stand for?

Thanks again,

Mixolidean