What exactly is a ground problem?

[tickyul]

Most cars have a negative-ground.

The ground in most vehicles, which is common with the negative terminal of the battery, is what supplies electrons to the various circuits. SO it is this basic loop : ground (battery negative) - load - positive (electrons return to the positive completing the circuit). If you have a bad ground (bad connection mainly) you have broken the ground - load -positive loop and no longer have a complete electronic pathway (circuit).

[CPinCA]

Just bought a 2015 Mazda CX5. It feels like I'm being electrically zapped from the floor and the pedals. Soles of my feet look and feel burned. Extra dark spots on the balls of the feet. Also, burning, skin darkened across top of the toes. Is this a ground issue? Is the car not properly grounded? Or some other electrical issue? Help.