HTTP: The internet king
The Hypertext Transfer Protocol, known as HTTP, is an application protocol for transmitting hypermedia resources, such as HTML documents. HTTP was designed within the framework of the Internet protocol suite, and it is the foundation of any data communication on the web.
Since HTTP is a client-server protocol, requests are initiated by the recipient. For example, when you enter a URL in your browser, it sends an HTTP command to the web server, asking it to fetch and transmit the requested content.
Usually, these HTTP requests are sent over an underlying and reliable transport layer protocol, with TCP/IP being the most commonly used. However, HTTP can be adapted to other protocols, such as UDP.
HTTPS: The secure version of HTTP
HTTPS means Hypertext Transfer Protocol Secure, which means that it is basically the secure version of HTTP. Under HTTPS, the communications between the browser and the website are encrypted by another protocol: TLS.
HTTP has been evolving over time: first, there was HTTP/1.1; then HTTP/2 was standardized in 2018 and HTTP/3 is now proposed to be the successor. HTTP/3 will become the third official version of the HTTP protocol. Although very similar to HTTP/2, it offers some significant advancements and changes to the underlying method of utilization. While still functional with TCP, HTTP/3 will actually be built upon QUIC, a Google/IETF hybrid which is foundationally a transport protocol developed upon UDP (more about HTTP/3 here).