HTTP (hypertext transfer protocol)
HTTPs (hypertext transfer protocol secure)
They are jargon terms of the Internet world. HTTP is an ARBITRARY protocol used to signify that you are trying to visit a certain website. You put HTTP in front of the web address together with the "://" symbols. For example, if you would like to visit "yahoo.com" for the sole purpose of viewing, streaming and browsing pages on the internet, you would most likely visit pages with http:// on the address bar. It is found on all websites. Browsers (Internet Explorer, Mozilla Firefox, Apple Safari) are defaulted to automatically put http:// or http://www. on the websites that you type on the address bar. That's why when you put "facebook.com" on the address bar, the browser will automatically put http:// so that it can connect to the internet and display the webpages. Http:// websites are prone to hacking and phishing.
HTTPs on the other hand is a SECURE version of HTTP. This means that you are trying to visit an ENCRYPTED website. This could mean that you are being asked to login and enter your password; that is if you are trying to access your online account or if you are entering a highly classified website (like government websites). All HTTPs websites are served by certain ENCRYPTION companies (e.g. DigiCert, Verisign). These companies provide the assurance that all communications that occur on the https website will be "encrypted," confidential and difficult to hack. HTTPs websites are usually seen after you have logged in to your online bank account, credit/debit card accounts, Facebook, Twitter, Yahoo, Google, eBay, Paypal, Amazon, etc. accounts and all other websites that may handle monetary transactions.
If you have the latest version of a browser, you can check what Encryption company is serving a specific website by clicking on the icon (usually that of a lock or key) on the left of the https:// on the address bar. Well, basically, Yahoo Answers is not encrypted.