CSR, Certificate Signing Request File (.csr)
The CSR Website file format
Digital website certificates may send out a signing request for the website visitor. These signing requests are stored in a CSR file. Certificate Authorities use CSR files to get a proof of identity for websites requiring a certificate. CSR files are created by the server where the certificate itself is located on. While your private key is to be kept secret, the public key is available in the CSR, allowing a Certificate Authority to create a SSL certificate.
Technical details of CSR files
CSR files help to identify the applicant of a website certificate. They contain block of text in it's encrypted form. The encrypted data includes several information about the client, like country and state, e-mail address and domain, organization and a public key. The CSR file works in the following way: A public key is included in the file. The according private key had to be given by the user (creating the signature) to verify the certificate.