system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What's activated charcoal?
gpt
First let's talk a little about what charcoal is -- charcoal is when you take wood and you heat it up without oxygen being around. The lack of oxygen is important because you don't want the wood to burn, you want to remove the water and other chemicals from the wood and leave behind the carbon. This oxygen-less heating process is called pyrolysis.

Activated charcoal or activated carbon is charcoal that has been treated to create lots of small holes/pores within the structure of the charcoal. These microscopic holes increase the surface area. This gives the activated carbon more area to bind to things and lock them up, which is why activated carbon is useful for purification purposes. Different chemicals bind to activated carbon better or worse than one another, and you can change those properties by treating/modifying the activated carbon in different ways.

You can make activated carbon using chemical activation using acids/strong bases/salts or physical activation with hot gases during pyrolysis.