In the past, when anybody created a website or web app, he/she was largely limited to a few select “web safe” fonts such as Times and Arial. If you deviated from these fonts, you were required to use Adobe Flash or to embed text in images, which introduced a whole new set of trade offs. For example, images aren’t semantic, cannot be translated into other languages automatically, and can be much larger in file size than text. In addition, text in images cannot be copied to a user’s clipboard, read with screen-reading software, or easily indexed by search engines.
Unlike Times and Arial, which are references to fonts installed on a user’s local machine, web fonts are served via a browser request (much like an image would be served). That means you can push any web font to a user’s machine. Users will be delighted when they realize these fonts behave just as any other text in Arial would behave.
Some example web fonts, offered by the Google Web Fonts service
The adoption of the web font technology has been rapid. Google Web Fonts now serves roughly 50 million daily requests, across roughly 800,000 unique websites, and is growing at about 30% each month. Here at Google, we’re excited about the potential for web fonts to change the very fabric of the web. Beautiful typography makes the web more pleasant to browse, expressive, and interesting.