What is HTTP?
Hypertext Transfer Protocol (HTTP) defines how data packets are communicated between a device and a web server and what actions a device and web server should take in response to the data packets.
For example, if you want to access the website lifehacker.com.au, you would have to enter HTTP which tells the web browser that this address is a web server. The device sends data packets communicated via HTTP to which the server responds back with data packets showing the website.
Nowdays, web browers automatically put the HTTP/HTTPS when you enter a URL without the HTTP/HTTPS. While you may not be able to see it, it is still there!
Why does HTTPS have a 'S'?
Some URLs have HTTPS instead of HTTP. Hypertext Transfer Protocol Secure (HTTPS) simply means there's a secure channel where the regular HTTP process has taken place but data packets are encrypted through public key infrastructure. Encryption involves a private key known by you and the web server and a public key obtained off the web, to ensure data packets can only be read by the sender and its intended recipient.
HTTPS is useful when transferring sensitive data such as personal information or money transfers.
For example, an online banking website, such as Commbank, would use HTTPS. If you were to do some online banking on the Commbank website HTTPS represents a secure channel for data packets to be sent directly from your device to the Commonwealth Bank's web servers. Information is encrypted and cannot be read by intruders such as hackers and can only be read by the bank and you.