Here we go!
VST = Virtual Studio Technology. Most popular format for effects by Steinberg.
VSTi = VST instrument. Same format but these are instruments. duh!
ASIO = Audio Stream Input/Output. A driver for Windows which reduces delay in sound and improves quality
ReWire = A gadget that allows you to use two DAWs simultaneously using one as a mixer and other(s) as a synthesizer/ instrument.
Side chaining = You use one sound to change another. Usually side chain compression or 'ducking': when normal compressor has gain detector and gain reductor on the same track, a side chained compressor has gain detector on one and reductor on other track. This means that when there's sound on the other track the other track becomes quieter.
Envelope = In an instrument it often refers to amplitude envelope and usually consists of 'Attack', 'Decay', 'Sustain', and 'Release'. This determines the way the volume of sound changes over time.
-Attack time means how long it takes from the moment a note is received in to sound reaching maximum volume.
-Decay time tells how long it takes for the sound to fade out completely while the note is on.
-Sustain means how long the sound stays on max volume while the note is on.
-Release time tells how long it takes to fade out completely after the note is released.
Automation envelope then again means the curve NavyBrony talked about:
NavyBrony wrote:Automation: Describes a change over time. Typically shown as a line on a track, and assigned to 1 or more effects. Depending on line position, the effects are changed...
Harmonics = Frequencies that sound consists of. For example when you play the A4 note (440Hz) using a saw wave there are also other frequencies above the 440 Hz. Depending on what frequencies are there and how many of them will give the sound that certain nature.
FFT = Fast Fourier Transform. It's a mathematical operation which has some applications in music. For example FFT display tells you what frequencies are present at current time and can be very useful when equalizing.
Bit depth = This is more of computer science but basically it means how accurately is the sound's amplitude handled. With low bit depths a sine wave starts to sound like a square wave. Bit depth reduction or amplitude quantisation is quite common and funny effect.