Named values for the visual decisions of a product — colours, spacing, type sizes, radii, shadows — stored once and referenced everywhere instead of being written out in each file.
Tokens are what make a rebrand or a dark theme a one-day change rather than a month of hunting hex codes. They also keep design and code in sync, because both sides use the same names.
We define tokens as CSS variables shared by the design file and the codebase, and forbid raw values in components, so a change to a token propagates through the entire product at once.