This document discusses the basics of (X)HTML tags. It explains that an (X)HTML tag consists of a name surrounded by angle brackets. Tags should be written in lowercase and most tags come in opening and closing pairs to label content. Elements are made up of opening tags, closing tags, and the content between them. Tags can be nested within each other and the first opened tag must be closed last. Some tags are empty and self-closing. Attributes add extra information to tags and their values are contained within quotes. Tags can have multiple attributes separated by spaces.

3. Anatomy of an (X)HTML Tag

11. Attributes