Which of the following best describes a mock-up?

A mock-up is a visual representation of a layout plan that demonstrates the design and user interface of a product or application without implementing any functional components. It helps to visualize the structure, layout, and functionality of the project at an early stage, allowing stakeholders to provide feedback on design elements and user experience aspects. This representation can include elements such as buttons, menus, and overall page layouts, providing a tangible preview of how the final product will look and feel. This is essential for gathering input before proceeding to development, ensuring that the final product aligns with expectations and requirements.

In contrast, a fully functioning version of software is referred to as a prototype or the final product. A functional database schema refers to the structure of a database, while a rough estimate of development costs involves financial forecasting rather than design representation. These options do not encompass the primary purpose and characteristics of a mock-up.