HTML stands for Hypertext Markup Language. Hypertext refers to the ability to turn a piece of text into a hyperlink (which we now call simply a “link”) that takes the viewer to another document. Markup language refers to the way HTML assigns semantics (purpose or meaning) and structure to specific parts of the document by “marking” them as a title, heading, paragraph, link, etc.
Document format examples
You can view examples of various document formats when you use the “Save As…” option in word processing software and look at the list of formats or types offered.
In order to save a document — as a file on disk, for example — the computer must disassemble the document and arrange it into a single stream of data according to the specific, standardized rules of the document format you are saving as. In order to open the document on another computer, that computer needs software (an application or program) that can understand the format the document was saved in.