A Certificate Signing Request (also CSR or certification request) is special file that you provide to a Certification Authority (CA), such as GeoTrust, Symantec and Comodo. It's used by the CA to generate, sign and issue a new digital identity certificate.
CSR's are usually generated directly on the server where you plan to host a secure website or application. Most servers come with the software libraries needed to generate SSL/TLS keys and CSRs. An example would be OpenSSL which nowadays comes pre-installed on most Linux distributions.
The CSR contains all the necessary information needed by the CA to authenticate your organization such as your domain name, business name and location.
When generating your CSR you will be asked for input. Below are some common fields with descriptions and examples.
The following characters should not be used when typing in your CSR input: < > ~ ! @ # $ % ^ / \ ( ) ? , &
Below is an example of what your CSR will look like.
-----BEGIN CERTIFICATE REQUEST-----
-----END CERTIFICATE REQUEST-----