What you actually bought
What this box is for, which generation it belongs to, and the one sentence that explains most of the confusion around it.
01 · 4 min
A whole guitar rig in one box, built by dropping blocks onto a grid and wiring them together. Whether it sounds right depends almost entirely on what you plug it into.
The short version
A compact floor processor with a 12x4 stereo grid, one amp and cab pair per preset, eight scenes and four channels in every block. Three footswitches with switchable layouts, and Fractal's Secret Sauce IV instrument input.
Is this the right guide?
If yours has nine footswitches it is an FM9, with a bigger grid and two amp and cab pairs. The Axe-Fx III is the rack version of that same larger engine.
The thing everyone gets wrong first
On a FM3, the question we see most is running out of room for a second amp.
The FM3 allows one amp and cab pair. Use the four channels inside that one Amp block to get four voicings instead.