Design libraries are collections of reusable design elements, such as buttons, icons, and typography, that help maintain consistency across digital products. They provide designers and developers with a set of standardized components, making it easier to create user interfaces and improve collaboration within teams. These libraries can be physical or digital, often hosted on platforms like Figma or Adobe XD. By using design libraries, teams can save time, reduce errors, and ensure that their products align with brand guidelines, ultimately enhancing the user experience and streamlining the design process.