RSAfootnote:[https://datatracker.ietf.org/doc/html/rfc8017] is a widely-supported PKI system. It is ubiquitous, but it is recommended to use newer systems (e.g. ED25519) for OpenSSH if all clients and destinations support it.
The key structures have references to the RSA notations in single quotes. You can find these enumerated in https://datatracker.ietf.org/doc/html/rfc8017#section-2[RFC 8017 § 2] or https://datatracker.ietf.org/doc/html/rfc8017#section-3.2[RFC 8017 § 3.2^]. See also the https://en.wikipedia.org/wiki/RSA_(cryptosystem)#Key_generation[Wikipedia article^].
It is *highly* recommended to use 4096-bit RSA if using RSA keys.