Block types include PGP MESSAGE, PGP PUBLIC KEY BLOCK, PGP PRIVATE KEY BLOCK, PGP SIGNATURE and the cleartext form that starts with -----BEGIN PGP SIGNED MESSAGE----- (§7). Optional armor headers follow the first line, and an optional CRC24 checksum line starts with =; RFC 9580 says new armor should not include the checksum and readers must not reject armor because of it.
It looks like PEM but is a different format: PEM labels name ASN.1 structures, armor names OpenPGP packet sequences, and tools for one will not parse the other. Cleartext-signed messages dash-escape lines starting with -, and trailing whitespace is ignored when hashing, a frequent source of confusion.