Shared parts with instructions
Think of a design system as a kit of interface parts with instructions for using them. It may include design tokens (named values for colours, fonts, and spacing), button and form patterns, writing guidance, and reusable code.
Designers may keep examples in a shared Figma file, while developers build matching components into the product. When teams improve a shared button, every screen that uses it can benefit.
Consistency needs judgement
A useful system covers accessibility and how parts behave during errors or loading, on small screens, and with a keyboard. A component library alone is not enough: teams also need guidance, ownership, and a way to add or revise patterns. Consistency helps, but a pattern should change when it no longer serves users well.