What are the keyid and finguerprint of a public key in gpg and apt-key?

https://superuser.com/a/931814/ says > Here follows an example command to use the GnuPG package's gpg command > to receive a key (-recv-keys) with the fingerprint 7CE8FC69BE118222: > > $ gpg --recv-keys 7CE8FC69BE118222 Are a key and its fingerprint different concepts? From manpage of apt-key: > apt-key export > > Output the key keyid to standard output. Are a key and its keyid different concepts? Are the keyid and fingerprint of a key the same concept? For example, we can first retrieve the key with

-shell
gpg --keyserver keyserver.ubuntu.com --recv-key E298A3A825C0D65DFD57CBB651716619E084DAB9

and then feed it to apt-key with

-shell
gpg -a --export E298A3A825C0D65DFD57CBB651716619E084DAB9 | sudo apt-key add -

Is E298A3A825C0D65DFD57CBB651716619E084DAB9 a key, the keyid of a key, or the fingerprint of a key? Why does it still work if I replace E298A3A825C0D65DFD57CBB651716619E084DAB9 with 51716619E084DAB9?