system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does teeth whitening/bleaching work?

I'm wondering if someone could actually explain how it achieves whiter teeth, as my teeth are somewhat stained due to heavy caffeine consumption (lots of tea). 

And also if there is any differences between whitening or bleaching.
gpt
Whitening is usually used to refer to the mechanical removal of stains by some sort of physical action, IE using abrasives in toothpaste that will scrub off surface stains on the tooth enamel.

Bleaching is breaking up stains via chemical action, essentially using a chemical agent to break the stains down into smaller molecules.