HTTPS stands for Hyper Text Transfer Protocol Secure, the secure version of http, the protocol for communicating data between your browser and the websites that you are connected to. https ensures that all such communications are encrypted.
For several years now technical experts have highly recommended the use of https instead of http for exchange of information between web browser and web server. But while the change to https in the browser is painless, there are significant additional costs to implementing https on a server. Given these, why is https so strongly recommended?