Prototypes are usually the next step in the product design process after creating mockups. Sometimes, there's no time or budget for mockups, and instead, UI designers create low-fi prototypes. They typically have color, typography, animations, and actual content. Prototypes are also interactive, allowing users to test the interface and interactions.

Prototypes don't represent the end product, but they're complete enough to show to users and stakeholders. They allow you to conduct final tests, fix minor issues, and hand over your designs to the development team.