CSS (Cascading Style Sheets) allows separation of design and content on web pages. It was created in 1994 and has become the W3C standard for controlling visual presentation. Using CSS provides advantages like faster downloads, streamlined maintenance, global design control, and cost savings through reduced bandwidth and higher search engine rankings. CSS can be applied through inline styles, embedded style sheets, or external style sheets linked via HTML. Resources for learning more about CSS include various websites documenting its capabilities and best practices.