HTTPS translates to HyperText Transfer Protocol Secure. It is used as an underlying code on the world wide web and defines how messages should be formatted then transmitted. Although it does compare closely to HTTP (HyperText Transfer Protocol) it has a layer of added security known as a Secure Socket Layer or SSL. With an SSL, all communication between your website and browser is encrypted.
Check out this blog on making your site secure.
Still need some help deciding which is better? Read this blog comparing HTTP and HTTPS.