system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What are the white spots on your fingernails and how do they get there?
gpt
The white spots on your nails are known as lesions. They are caused by shock or damage while the section of nail is still growing, and also by air bubbles getting trapped behind your nail. Sometimes direct pressure to the finger/toe can cause these as well.

Basically, after being subject to damage the cells forming the keratin nails generate calcium-deficient, opaque tissue giving it a stark-white appearance. Under normal circumstances small dots of discoloration appear but if you develop issues with your liver or kidneys then white bands of discolored keratin will form.

It's the same process that gives your teeth those nasty white spots around braces.