Grounds are like the sewer or septic system in a municipal water supply- - - -they get the water back into the earth it came from. Ditto for auto electrics- - - -the electrons need a low-resistance path back to the battery to complete the circuit.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!