Certificate Signing Request
A Certificate Signing Request (CSR) is a file that contains a public key, along with some metadata which typically includes an organization name, domain name, etc.
A CSR file is intended to be sent to a certificate authority, who can then (after performing any required validation of the sender's identity) generate and send back a signed certificate. Note that the certificate authority does not need to know the certificate's private key.
The most common CSR format is PKCS10.