HTTPS indicates Hyper Text Transfer Protocol with Secured Socket Layer.If a website has this indiaction then it means that the website includes the necessary protective layers.If you're going to run an online store or ecommerce Web site, you should be aware to include this provision to safeguard your visitor's personal and payment information.
HTTP sends the data collected over the Internet in plain text. This means that if you have a form asking for a credit card number, that credit card number can be intercepted by anyone(hacker).
When you set up the web page with https the website passes over the secured layers and encryption process.Hence the user's data are well protected.
There are several service providers like XnYnZ.com who authenticated the website with a https staus with their SSL Certificates service.