system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happens to a charger that's plugged into a power outlet but doesn't have a device attached?

For example, if I plug in the power brick for my computer into a power socket, but I don't attached the charger to my computer. What happens to the brick while it's on "idle?" Is it somehow being damaged by me leaving it in the power outlet while I'm not using it? 

Edit: Welp, I finally understand what everyone means by 'RIP Inbox.' Though, quite a few of you have done a great job explaining things, so I appreciate that.
gpt
Wall adapters and chargers are almost always AC to DC adapters. What they do is take the electricity in the wall and change it from whatever periodically-changing voltage is standard in your country (AC) into a constant voltage (DC) of a certain amount. A simple way to do this is to change the voltage with a transformer and then force it to always move in the same direction. A more complicated (but more efficient) way to do this is to store it as a magnetic field for a very small fraction of a second and then bring it back as the correct voltage. In either case, the final voltage is regulated by capacitors which store energy and try to keep the voltage steady.

Well, that's the ELI5 version of it.

Anyway, theoretically an AC to DV converter circuit shouldn't draw any energy out of the capacitors which keep the voltage steady when there's nothing plugged into it, but in reality it's not so simple. The components that make up the circuit are imperfect which means it will always use a little bit of energy when plugged in. In addition, many power bricks have a LED on them which shows that it's plugged in, meaning that you always have some tangible amount of power being used.

TL;DR: It will always use a small amount of power when plugged in, but you won't harm the adapter by doing so.