A 14500 battery is known as a lithium ion battery although the actual numbers refer to the size of the particular battery. For instance a 14500 battery is (first 2 numbers diameter) 14mm dia. (next 2 numbers length) 50mm L. and I believe the last number refers to the cylindrical shape of the battery 0 cyl. =14500. Although I'm not %100 sure about the last number, that's the gist of it. Also AA primary batteries like the ones you throw away after use are pretty much the size of 14mmDx50mmL same as the li-ion 14500s. When referring to AA batteries it's usually a alkaline battery or maybe even a lithium non rechargeable (not lithium-ion) battery. Many times you can't exchange a AA 1.5v battery for a lithium ion 4.2v=(fully charged) because of the extreme voltage differences, some flashlights are able to use both types of batteries if they're designed to do so. A protected battery refers to a protection circuit added to a lithium ion battery designed to cut the battery power if the battery is overcharged, over discharged, short circuit, over amperage draw. The button top is the little round nub you'll see on the top of an AA alkaline battery, but they're also added the the tops of some li-ion batteries as well, a flat top is just that, no button (button top) has been added to the top of the battery. A nimh battery is another chemistry of rechargeable batteries that can be used in devices that also use alkaline batteries with lower voltages in the 1.2v range and higher when fully charged, they can be a very good option to replace primary (throw away) batteries.