Content should be written for the lowest common denominator of your target audience. If you are writing for someone who writes web documents all day then you can expect them to know what html is in great detail. If you write for plumbers they might not know what html is, and so you may need a couple paragraphs to define what it is. (I'm not sure why plumbers would need to know what a html tag is, but if you expect them to read a document where html tags are referred to you better define html in enough detail that they understand it)