system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what’s the difference between AA and AAA and other batteries? Why do we have a bunch of different ones?
gpt
They are sizes.

Back in the day, batteries came in size A, B, C, D, etc.

A being the smallest, and because they couldn’t make batteries that were smaller at the time, it was fine.

But, as tech got better we COULD make batteries smaller, so what is smaller than A? AA, then AAA, then AAAA.