A Certificate Signing Request (CSR) is required in case you wish to acquire an SSL certificate which will encrypt all of the payment and account info which are exchanged between your site and its clients. 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, etcetera. Based upon this code, a registered SSL vendor issues the certificate, which is digitally signed with the vendor's private key to recognize that they're a reliable issuer. At the time of the CSR generation, a unique private key is also created and the set up of the SSL involves all four codes - the two keys, the certificate as well as the CSR. Then, you will be able to use a URL that begins with https:// for your website instead of http:// and the site visitors will be able to view the info that you have provided for the CSR using their web browsers.