SSL protects information by encrypting data between two servers. Only the host computer can decrypt the data and only the client computer can verify the server certificate. If the session is interrupted for any reason, the session is broken and must be reestablished. Sites that implement the SSL/TLS protocol display a padlock icon in the address bar.
This is important because the information you send on the Internet is passed from computer to computer to get to the destination server. Any computer in between you and the server can see your credit card numbers, usernames and passwords, and other sensitive information if it is not encrypted with an SSL certificate. The validation of this certificate is for a year. After that period you need to renew it and the fee is the same.