Each component deals with a different aspect of web design, Html deals with hands on information, including words, paragraphs, headers, sections etc. CSS deals with aesthetic and style, such as font size and color. DOM is a gateway to all elements on your website, and can be used to manipulate the elements using HTML but also other languages (like Javascript)
Boxifying design deals with seperating sections of a draft web design piece into different sections, similar to an excel spreadsheet, except you must define the boxes using the div function. This serves to simplify the construction of the website.
Box Model refers to the layout. Every header, navigation menu and body can be segmented into boxes. Any of these boxes can be stylized through CSS.