Word processing program. Window's Notepad or MAC Simple Text will do for now. Written in a simple text language. It is NOT a computer language. This is important, because of the limitations of previous programming languages that required certain steps to be followed.
Text is what is used for writing.
You will find that it is very simple text. Mark-up is what you do. Write in plain English and mark-up what you wrote. HTML is indeed a language. A very simple language.