Google recently announced that they were using https/ssl as a signal for rankings. Meaning, sites that used HTTPS/SSL would improve in the rankings. Now at the moment, there is no need to panic if you don't have ssl enabled. It's only being used as a very small signal. You probably won't even notice a difference. But google has definitely made clear it's intention and will place more importance on secure sites in the future.
In non technical terms, a site with SSL enabled is delivered to the visitor encrypted. And the connection between the user and the website is encrypted. This means that your traffic can't be intercepted. For regular sites such as a blog it's not that important. But for web apps (something like Twitter for example) if it wasn't served over HTTPS a users password could be intercepted by someone monitoring your internet connection.
Having everything encrypted is a good thing and google would like to see more of the internet work like this.
How to start using HTTPS on your site
There are two ways, the first involves purchasing an SSL certificate from somewhere like NameCheap or Godaddy. You then need to install the certificate on your server. I've gone through this process many times and it's always an absolute bitch.
The other option is to use Cloudflare. They offer SSL for free. And installation is much easier. You just point your nameservers to cloudflare after signing up and the rest is automatic.
This isn't something you need to worry about this instant, but you should start thinking about adding SSL to your site. It will matter in the future.