Ohms are a measurement of resistance. The higher the coil's ohm reading, the more resistive it is - it physically restricts the natural current of the battery. This means less stored energy being used, thus more battery life at the expense of power. The lower the resistance, the more freely the battery can drain; so, more power at the expense of longevity.
The classic example is a bucket of water with a hose attached to it. Pinch that hose and it'll take forever to drain, thanks to the narrow stream choking out. Unpinch the hose and it pours out freely, strongly... and quickly.
Pull out the hose and you are effing WET my friend, so please do heed the above and educate yourself. Wet in this analogy is crispy in real life.