A Certificate Signing Request (CSR) is required in case you would like to acquire an SSL certificate which will encrypt all the payment and login information which will be exchanged between your site and its customers. The CSR contains info about the website plus its owner in Base64-encoded form - website address, physical address plus e-mail, company name and unit, etc. Based on this code, a licensed SSL vendor gives you the certificate, that's digitally signed with the vendor's private key to identify that they are a reliable issuer. At the time of the CSR generation, a unique private key is also generated and the set up of the SSL involves all four codes - the two keys, the certificate plus the CSR. Then, you'll be able to use a URL that starts with https:// for your site rather than http:// and the website visitors will be able to view the information that you've provided for the CSR via their Internet browsers.