SSL is used to secure credit card transactions, data transfer and logins, and more recently is becoming the norm when securing browsing of social media sites.
SSL Certificates bind together:
A domain name, server name or hostname.
An organizational identity (i.e. company name) and location.
SSL Certificates protect your sensitive information such as credit card information, usernames, passwords etc. It also:
Keeps data secure between servers
Increases your Google Rankings
Builds/Enhances customer trust
Improves conversion rates