What is SSL Certificate?

Secure Sockets Layer (SSL), are cryptographic protocols that provide security and data integrity for communications over networks such as the Internet when exchanging sensitive information between a website and the client.

SSL technology is embedded in all popular browsers and engages automatically when the user connects to a web server that is SSL-enabled. It's easy to tell when a server is using SSL security because the address in the URL window of your browser will start with https. The "s" indicates a secure connection.

When your browser connects to an SSL server, it automatically asks the server for a digital Certificate of Authority (CA). This digital certificate positively authenticates the server's identity to ensure you will not be sending sensitive data to a hacker or imposter site.

SSL can be effectively used to protect client's sensitive information, like credit card, bank account number, insurance number, and other personal information from being hijacked. 

One thing need to be noted is that SSL can only protect data during the transmission between web site and client.  It can not protect data stored inside the web site, like database or file system.  Other techniques may need to be deployed if required.