A home for design assets.
Design system tokens are the style values of UI elements such as color, typography, spacing, shadows, etc., that are used across products and capable of being converted to a format for any platform (web, mobile, desktop). Tokens are building blocks of the design system—think of them as sub atoms, the smallest pieces of style values that allow designers to create styles for a product.
https://xd.adobe.com/ideas/principles/design-systems/what-are-design-tokens/