A recharger is a machine that puts power back into a battery. You plug it in, connect the battery or the device, and the battery fills up again — phones, tools, cameras, car batteries, all the same idea. Though actually, in everyday English people almost always say charger, not recharger. Recharger turns up on some boxes, in older writing, or when a speaker wants to stress the ‘again’ part (re- = again). It is the same object: the little block and cable by the bed, or a bigger dock for a drill battery. Nobody will be confused if you say charger in a shop; some people may blink at recharger, not because it is wrong, but because it sounds a bit extra.