Design tokens: the details
Instead of writing a color like #FF5A1F in a hundred places, you define it once with a name and everything else references it. The term originated in Salesforce’s design system in the mid-2010s. Tokens are usually organized in layers: primitive values (the palette), semantic tokens (what each value is for: background, text, border) and sometimes component tokens.
The benefit shows when things change. A dark mode, a sub-brand or a contrast fix for accessibility becomes a change of values, not a search through the whole codebase. Tokens also carry the same identity to web, iOS and Android from a single source. A W3C community group maintains a common format for exchanging them between tools.