bought a load of stuff from madvapes to make a bunch of wood box mods and happened to click on one of the USB breakout boards. what is this thing used for? is it for charging batteries or just providing a way to plug my mod into a usb slot to power it? if its for charging batteries, can i leave a 18650 in the mod while its plugged in to charge? i know this is probably a dumb question but ill never know if i dont ask.

my new mod i made by the way.

my new mod i made by the way.