A more thorough explanation:

A thumbprint is a type of fingerprint. It is the unique pattern of lines on the tip of a person's thumb. No two thumbprints are the same.

Thumbprints can be used in criminal investigations to identify suspects. When a person is arrested, their thumbprint may be taken as part of the booking process.

For example, if a detective finds a knife at a crime scene, they may look for thumbprints on the handle to try and identify who used it.

Thumbprints can also be used for security purposes, such as unlocking a phone or accessing a secure building.

Overall, thumbprints are a useful tool for identifying individuals and can be used in a variety of settings.