HTML hypertext markup language.
hypertext: (linear) text that has links to other texts, forming a web of interconnected documents.
markup language: notation that indicates the structure of a document.

HTTP hypertext transport protocol.
protocol: the rules and message formats used by networked computers to communicate.
HTTP is the part of the Internet protocols (TCP/IP) used by web browser (client) and web server to get web pages.
Browser sends a Request to a server for a "resource", server sends the Reply with the resource.

URL: universal resource locator. Internet address.
with all parts being optional.
Protocol is HTTP by default.
Port is 80 by default. Sometimes 8000 or 8080 is used for a caching web server.
Secure, encrypted HTTP is protocol https:// which uses port 443.

Web page Layers

  1. content (text & images)
  2. structure: HTML. What it is.
  3. presentation: CSS. How it looks, how the elements are laid out.
  4. behavior. How it interacts, if any.