In Lichtlaerm’s words:

With all the fine sonic terror crafted on your instruments, there comes all sorts of unwanted noise. With every parameter of this gate defined by an envelope-follower, this is the most transparent solution you can get on the market! The gate reacts super fast to any change in your playing-style: from staccato to long sustained notes for a singing lead-tone: no problem!

The Key and the Gate is usable as a simple noise gate, by connecting the gate to the top-mounted in- and output, but the real magic happens when you make use of the key-feature:

Connect your guitar directly to the side mounted jacks and follow your usual signal chain from there. The pedal splits your signal internally and uses your unaltered guitar signal as a reference for its gating: no tone sucking, no loss of sustain! As the gate uses your pure guitar signal, you can leave it always on - it really doesn't care whether you're on your clean or dirt channel or what ever dirt pedals you put in between the key and the gate.

It's also super easy to dial in: One knob - that's it!

You can also inject any other signal into the key-input to control the gate, giving you unlimited opportunities for side-chain operation in the studio or even using it as a weird tremolo by connecting it to a LFO!