I go through a lot of batteries. I maintain a good supply of AAA, AA, C, D and 9 volt batteries with a couple of of various cell configurations for the various things I use that require them. Additionally, I have acquired a few AAAA batteries purchased in error. In particular I like a flashlight handy with a fresh set of D batteries installed.
I use batteries as a manner of convenience and to accessorize myself with various technology I utilize. I would have to say that my cell phone and two main flashlights are the biggest need I have personally.
Batteries are containers comprised of one or more chemical cells which are manufactured such that the chemical energy they contain is converted into electricity for use as a source of power. We refer to such chemical to electrical conversion as "battery power" and it makes a lot of the new era gadgets operate for us ... particularly those cell phones so many of us have become fanatical about.
Today is National Battery Day. It goes down each February 18th. I suppose it's a function of everything and everyone wanting their own "day" as it were.
Without batteries we would be slaves to the electric socket to engage technology by and large. Thus, batteries give us the ability to be portable without permanent attachment to some less than mobile power source.
They really are a marvel even with their explosions and other mishaps and misadventures likely due to how they are treated during operation.
My only qualm with batteries have to do with recycling them as my local jurisdiction can't even handle anything "battery" in the recycle and so I am forced to place spent batteries in the trash.