An SSL Certificate is a digital certificate that authenticates the identity of a website and encrypts information sent to the server using SSL technology. Encryption is the process of scrambling data into an undecipherable format that can only be returned to a readable format with the proper decryption key. Your SSL Certificate serves as an electronic "passport" that establishes an online entity's credentials when doing business on the Web. When your visitors attempt to send confidential information to your server, their browser accesses the server's digital certificate and establishes a secure connection. An SSL will also help you in google search results according to google!
Your SSL is the only product that will autorenew earlier than the due date; at least one month earlier. This is because your SSL is the only product that MIGHT need you to re-activate it. You should get your SSL for the longest possible term to avoid re-activation on a yearly basis.