A chicken's nail is very similar to a cat or dog's nail. There are blood vessels and nerves in it, called the quick. You can see the pinkish quick in white transparent nails. Trim the tip of the nail without touching the quick. It's better to remove multiple tiny pieces rather than risking to cut in the quick. If you do by accident cut in the quick, use the styptic powder to stop the bleeding.
How to trim chicken's nails