SSL Certificate, stands for Secure Sockets Layer Certificate, and it is the standard security technology for creating an encrypted link between a web server and a browser. This link ensures that all data passed between the web server and browser remains private and integral. SSL is an industry standard and is used by millions of websites in the protection of their online transactions with their customers. In order to be able to generate an SSL link, a web server requires an SSL Certificate.
When you choose to activate SSL on your web server, you will be prompted to complete a number of questions about the identity of your website (e.g. your website's URL) and your company (e.g. your company's name and location). Your web server then creates two cryptographic keys - a Private Key and a Public Key. Your Private Key is so called for a reason - it must remain private and secure. The Public Key does not need to be secret and is placed into a Certificate Signing Request (CSR) - a data file also containing your details.
Your web server will match your issued SSL Certificate to your Private Key. Your webserver will then be able to establish an encrypted link between the website and your customer's web browser.