Wireframes make the design process iterative

The iterative design process is an approach that designers and developers use to continually improve a product's design. It includes creating prototypes, testing them, analyzing team and user feedback, and refining the product as a result. While any part of the design process can be iterative, it's worth starting as early as possible — full design mock-ups take more time to be reworked than simplified wireframes.

Wireframes let you test and improve 4 things — the structure, layout, content, and functionality of your website or app, without touching the creative and branding aspects of the product.