An RSA PRIVATE KEY file is a digital file that you can use to DECRYPT messages sent to you. It has a public component which you distribute (via your CERTIFICATE file) which allows people to encrypt those messages to you.

A Certificate Signing Request (CSR) is a digital file which contains your public key and your name. You send the CSR to a Certifying Authority (CA), who will convert it into a real Certificate, by signing it.

A Certificate contains your RSA public key, your name, the name of the CA, and is digitally signed by the CA.

BROWSERS that know the CA can verify the signature on that Certificate, thereby obtaining your RSA public key. That enables them to send messages which only you can decrypt.

An RSA private key file is a digital file that you can use to decrypt messages sent to you. It has a public component which you distribute (via your Certificate file) which allows people to encrypt those messages to you.

A Certificate Signing Request (CSR) is a digital file which contains your public key and your name. You send the CSR to a Certifying Authority (CA), who will convert it into a real Certificate, by signing it.

A Certificate contains your RSA public key, your name, the name of the CA, and is digitally signed by the CA.

Browsers that know the CA can verify the signature on that Certificate, thereby obtaining your RSA public key. That enables them to send messages which only you can decrypt.