An alkaline battery is a primary battery (non-rechargeable) often used in electronics applications requiring heavy currents for long periods of time (e.g. CD players and radios). Alkaline cells overcome some of the problems with carbon-zinc batteries by using potassium hydroxide in place of ammonium chloride in the electrolyte. Potassium hydroxide is a base or alkaline material, hence "alkaline" batteries.
Alkaline batteries have a much longer shelf life and perform better under drain and in cold weather than their carbon-zinc counterparts. They also avoid the use of the zinc-corroding ammonium ions and do not produce any gaseous products. Typically, they can deliver 50-100% more total energy than carbon-zinc batteries of the same size; hence their popularity in consumer applications.