The picture above was made to understand the concept of gpg key structure, but it could be theoretically wrong because it was drawn with my personal interpretation. It seems that further updates are needed.

A GPG key can also add a subkey and has the following properties as information to distinguish each key.

fingerprint

Unique hash value for key discrimination

keyid

The short-handy version of fingerprint is keyid

keygrip

Unique hash value to find a key pair