Communication is emotional. Words written by authors such as Upton Sinclair, Harriet Beecher Stowe, and Thomas Paine have moved people to tears, sparked movements, and changed the course of nations.
How words are presented visually affects how readers perceive them. Matching the right font with the right message is the role of the designer.
When conveying a serious message, for example, a designer should obviously avoid using an informal font like Comic Sans.
Text is used throughout a page for different purposes: headings, subheadings, navigation menu labels, main content, figure captions, small print in the footer, and so on.
CSS allows designers to make compelling type for all of these purposes.