As very well definded in Adobe Spectrum's design system:
Design Tokens are all the values needed to construct and maintain a design system — spacing, color, typography, object styles, animation, etc. — represented as data. These can represent anything defined by design: a color as a RGB value, an opacity as a number, an animation ease as Bezier coordinates. They’re used in place of hard-coded values in order to ensure flexibility and unity across all product experiences.
Design Tokens are directly integrated into our component libraries and UI kits. They cover the various options of platform scales, color themes, component states, and more.
The best tools for design tokens.
Learn about Design Tokens by reading some of the best content out there.