First, what is the difference? You’ve probably noticed sites that are supposed to be secure like banks and sites taking your credit card information have that https:// at the beginning of their URL instead of just the http:// like other sites.
According to GoDaddy:
HTTP, or hypertext transfer protocol, is the way a Web server communicates with browsers like Internet Explorer® and Mozilla Firefox®. HTTP lets visitors view a site and send information back to the Web server.
HTTPS, hypertext transfer protocol secure, is HTTP through a secured connection. Communications through an HTTPS server are encrypted by a secure certificate known as an SSL. The encryption prevents third-parties from eavesdropping on communications to and from the server.
NOTE: Only servers that have their own SSL can create HTTPS connections. A site’s visitor cannot encrypt the connection.
If you have a hosting account with an SSL encrypting its connection, you can automatically redirect visitors to the HTTPS version of your site
With Google recently announcing that it would give preferences to HTTPS and the added security, you may be thinking about moving your site to the more secure connection. Here is a great document by Chris Palmer to walk you through the steps:
Also, if you’re concerned about site speed with HTTPS, you might want to take a look at this website: http://www.httpvshttps.com/