The document discusses CSS (Cascading Style Sheets) and how it can be used for web development. It covers some key points:
- CSS is used to define styles and layout of HTML elements. External style sheets allow changing appearance across pages by editing one file.
- CSS rules have selectors that point to HTML elements and declaration blocks with properties and values to style those elements. Common selectors include element, id, class, and grouping selectors.
- Styles can be defined internally, in an external .css file, or inline. The document demonstrates color, text alignment, backgrounds, and other basic CSS properties.