amps are amount of current of energy or how high the flow is
watts are a measurement of energy

ok u need to get an understanding of how electricity flows, uve got ur battery its got 2 sides one positive one negative, from the positive end it starts breaking off to different fuses, relays, systems, and subsystems, anything that draws power (uses energy then needs to be grounded to close the loop (have a wire going back to the negative side of the battery). all cars (as far as i know) use the chassis or body of the car as a ground and then have a wire connected to the negative battery cable off of the chassis. resistance is caused by bad connections, worn wires, wires that are too thin for the amount of amps going thru them, or something is too far back in the circuit loop (has too many components [systems or subsystems] off of that particular wire b4 being grounded, im trying to think of a way of explaining this. ok this is kinda out there but:
top of the waterslide is the positive connection of ur battery
pool at the bottom is the negative,
tubes are wires

think of a water slide (which is a certain height in there air that Needs to get water to different areas (those areas needing that water or power) which ultimately ends up in a pool then that pool pumps water back to the top and it starts all over,

starting up high the water is rushing down a tube, the tube then breaks off and heads in different directions, breaking off into different directions does not slow down the energy of the water, but the steeper the tube downward the faster the water moves and the opposite applies, the slower the water moves the more energy is lost (resistance is built up), with damaged tubes leaking water (Power is lost), with a tube not getting water to where it has to (short circuited) the system will not get power and the water will just fall to the pool causing the system to not work at all. so the steeper tubes or smaller connected areas will get more of a current of water than those longer tubes, long tubes the will have more resistance and will eventually get the water thru but the current will have slowed due to resistance.

thats kinda confusing, by creating better grounds, ur allowing the energy to come back to the battery creating a better circuit with less resistance in effect making whatever is drawing the power stronger, ie lights, radio, spark plug ignitions, etc.