What do each of the $ lines mean, is there a legend somewhere?

[werdh2ofall (Drew)]

I’m working on a mac running venturi on a chinese diode (LDHTHOPI)

[berainlb (PY)]

Are you referring to GRBL $ configuration values?

If so, here’s a reference:
grbl/settings.md at master · gnea/grbl · GitHub

[ednisley]

@berainlb

GRBL $ configuration values

Aaaaand, of course, everybody who writes GRBL-based firmware (*) adds unique parameters with no documentation anywhere (that I’ve seen): when the parameter you seek isn’t in that list, it’s not GRBL’s fault.

(*) Which, depending on the circumstances, can be pronounced “rips off GRBL firmware without paying attention to the GPL”.

[DaveK-OR (Dave Keasey)]

Another very good reference can be found here:

http://linuxcnc.org/docs/html/

Although it is oriented towards LinuxCNC implementation, there is a very good section on G-Code, and it provides detail that many of the other G-Code references ignore or gloss over.