I think at this point in the World Wide Web, we're all aware that "HTTP" is the beginning of most web addresses, even if we're not sure what it means. Even fewer of us are aware of what "HTTPS" means or why it might be better in spite of the Muppet-like arm waving and shouting of security types about the benefits of using HTTPS in any situation where a user is transmitting data.
If you do want to learn more about why and when HTTPS is crucial, this article has a fantastic explanation. The short of it is the "S" is for "Secure," which is what you want any time you're having a two-way conversation with a website. That "S" means your data is encrypted in transit so that people can't eavesdrop on your conversations quite so easily. All sorts of problems can happen when people can peek in on what you're doing, especially when passwords or money are involved.
Apple can have great moments of security savvy immediately followed by baffling lapses. The lack of HTTPS with the App Store was clearly one of the latter, as both money and passwords are involved when going to Apple's App Store. But at least that change has now been made and the App store is now using HTTPS. So now you don't have to cross your fingers and hope that your transmission doesn't get hijacked if you need to buy an app while you're at the airport or friendly local coffee shop.