A Certificate Signing Request (CSR) is required when you want to acquire an SSL certificate which will encode all the payment and login info that are exchanged between your site and its visitors. The CSR contains info about the site plus its owner in Base64-encoded form - web address, physical address as well as e-mail, company name and unit, and the like. Based upon this code, a licensed SSL vendor issues the certificate, that's digitally signed with the vendor's private key in order to identify that they're a dependable issuer. At the time of the CSR generation, a unique private key is also created and the set up of the SSL involves all of the 4 codes - the two keys, the certificate plus the CSR. Then, you'll be able to use a URL that starts with https:// for your website rather than http:// and the site visitors will be able to view the information that you have provided for the CSR using their web browsers.