... when I sit at a computer I am a total MIDIot.
No you're not.
MIDI was never intended for normal human beings to understand. It's a protocol for musical machines and it was originally devised when data rates were slow and latency was important. It still has a lot of baggage from those days. There is absolutely no shame in finding MIDI hard to understand. You are a very long way from alone!
I have a slightly different interpretation from Mario's about VST vs VSTi.
VST is any plugin that conforms to Steinberg's VST standards.
It can be an instrument, an effect, an oscilloscope or similar, or possibly some combination of several.
VST
i is just a handy way to quickly say "this is a VST instrument".