You can program the ignition to fire at the optimum point depending on the revs at a given point rather than it being set to one single degree across the board. There’s other bits a bobs you can play about with as well. That’s the very very very simple version. Obviously it’s way more complex, but it’s about having a degree of freedom with timing.
I haven’t tried it (it’s not legal for KZ) but I was told it makes a a significant difference laptime-wise as it’s one of the major limitations of a KZ. You gain bottom end while extending top end rev range, as you break away from the compromise of a static ignition point.
I believe it’s non-programmable, based on a pre-determined curve that apparently works very well with the TM engines. You just need to bolt it on and index it correctly. I know of the option as some used it to cheat in local races (and got caught) as you can disguise it to look almost exactly like the regular one. The one @Alan_Dove shared looks much more sophisticated and adjustable