Slave connectors allow you to jumper one vehicle to another; much simpler than having to open the hoods and wrestle with cables with their typically corroded clips.
Everything automotive, and most gensets, have 'em. Just make sure you keep the connector capped when not in use 'cause it's direct connected to your batteries.
How many pins in your under dash plug? Multi-pin is diagnostic, one or two pins are an accesory outlet for things like a trouble light.
Reading the dash ten (operators manual) is always helpful as it tells you 99.9% of EVERYTHING you need to know for daily operation.
Get a hard copy to carry in the vehicle too; you aren't always going to be close to your computer.
For more reading, the 24Ps are great for parts break-down.
Carry all in a GI 'document bag' and you're in business.