@leonardshelby OK, it's so you can power the laser from a separate supply because the current is too high for the Mana board to source. It has nothing to do with PWM-to-TTL conversion.
The colors are misleading in that picture but the connections are accurate so I guess colors don't matter. Usually power (+) is red, ground (-) is black and the TTL signal (s) is yellow, not as shown.
It is connecting 12VDC power direct to the laser and getting the ground and TTL signal from the Mana, no different to running a couple of wires yourself but I guess this makes it plug and play which is convenient.