A mockup is a scale or full-size model of a design or device used for teaching, demonstration, design evaluation, promotion, and other purposes. Designers use mockups mainly to acquire feedback from users. Mockups are an integral part of the design process in product development.

Pros:
1. Visualization: Mockups provide a realistic visualization of the final product, helping stakeholders to understand the design concept effectively.
2. Feedback: They allow for early feedback from clients and end-users, which can be incorporated into the final product, thus saving time and resources.
3. Cost-Effective: Making changes to a mockup is more cost-effective than changing a finalized product.
4. Error Identification: They help identify design flaws and errors early in the design process, leading to a better end product.
5. Marketing: Mockups can be used in marketing materials and presentations to showcase the design to potential clients or investors.

Cons:
1. Time-Consuming: A detailed mockup can be time-consuming, especially for complex designs.
2. Limited Functionality: Depending on the fidelity of the mockup, it may need to demonstrate the final product’s functionality fully.
3. Over-reliance: If stakeholders become too attached to a mockup, there is a risk of over-reliance on a particular design concept.
4. Misinterpretation: Stakeholders may sometimes need to be more accurate with the purpose of a mockup and mistake it for the final product.

In conclusion, mockups are essential in the design and development process, visually representing the final product and enabling stakeholders to provide valuable feedback. While they have limitations, the benefits of mockups outweigh the drawbacks, making them a valuable asset in the product development lifecycle.