SSL stands for Secure Sockets Layer, and it is the standard security technology for establishing an encrypted link between a web server and a browser. All web sites should now have one, as your site will start to be ranked down by Google if it doesn't.
Previously SSL was mainly used for ecommerce sites, to provide an extra layer of security, but now many sites are capturing customer data, such as email addresses, it really becomes a requirement for every web site.
Many website platforms will be able to provide the necessary certificate as part of their service, but if not there are many other providers who would be pleased to do this for you.
If you use Chrome as your browser, you will have noticed an additional bit of text before the url, which shows if the site you are viewing is secure. Take a look at this next time, before you start giving away your personal information to a site that isn't secure!
So if you want to be https get yourself an SSL certificate for your site now!