VST is an audio plugin standard developed by Steinberg (the ones who made Cubase). VST plugins can be both effects, MIDI effects or instruments. Instruments are sometimes called "VSTi". Automation is achieved using MIDI commands, but you might not even see this depending on the host application.
You can use VST effects and instruments from within Buzz using the bundled Polac's VST package which offers many features that outcompetes even many commercial VST hosts.