Somewhat hilariously, having perused your first two links, and followed the link from Sweep to Ferris, I still find myself having no idea how any of this works. (But I know a lot about how the firmware and PCB layout is designed!).

I have a charachorder. It's similar to music theory where you can hit individual notes to make up a chord. With chording you hit multiple keys usually that are part of a larger word and it outputs the associated word. This means instead of having to hit every individual key in sequence to type out a phrase one character at a time, you hit multiple keys at once to output words at a time. In the time it takes to output a single character on a keyboard someone on a charachorder did the entire word already. The longer the word the more speed is gained from this. It takes a lot of time to learn though, like a solid month of practice just to get near speeds I have with normal keyboard. Significantly helps with hand strain from typing all day due to requiring far less hand movement.