HyperText Transport Protocol is the communications protocol used to connect to servers on the World Wide Web. Its primary function is to establish a connection with a Web server and transmit HTML pages to the client browser.
Hypertext Transfer Protocol abbreviated as HTTP is a protocol which contains a set of rules and convention for transmitting and exchanging files via the internet. It is coordinated by WWW i.e. World Wide Web Consortium. A file can be any file like text file, image files, query results or anything else. HTTP is a request and response standard of a client and a server. The basic communication is followed by sending a request from the client side and getting a response from the client side. Here HTTP servers are the Web Servers.
HTTPS stands for Hyper Text Transfer Protocol Secure. A web site starting with https//: means that your computer is talking to the website in a secure code that no one can eavesdrop on. The primary difference between http and https is with the default port which is 80 for http and 443 for https.