A Prototype is a simulation of the final product, focused on how the product will look like and how users will interact with it. Although you don’t release a prototype to the market, you can receive feedback when testing it with users. A prototype is a cheap and fast way to collect feedback and evaluate the user's experience, before developing the final product. 

Because, through prototype, you can collect data and map improvements in a low-risk environment. It is possible to test and validate hypotheses before they are released to the public. If a hypothesis is launched immediately, your business is at great risk of failing real customers and taking losses that could have been avoided.

Choosing a prototype depends a lot on the hypotheses to be tested and the resources available. Low fidelity prototypes, for example, are simple prototypes, without many details and far from what the final product will look like. They are used at an early stage, consume little time and resources, and can already test simple flows. It is used when you need a quick answer to a relatively simple scenario.

On the other hand, High fidelity prototypes are very similar to how the final product will look. They are often interactive, with users being able to browse and test different flows. This prototype is used to validate relatively more complex hypotheses and find errors from the smallest details, to doubts with texts and problems in more complex flows.

Wireframe is a basic, low-fidelity representation of the layout. The goal is to represent the main ideas, not the details. Wireframes are the skeleton, the initial structure of the project.

A mockup is a visual representation of the product. It is not interactive, but a static, high-fidelity view. The mockup helps, for example, to visually show and explain what the product is like.

A prototype, in turn, involves interaction. It is used to simulate the functioning of the final product and validate hypotheses, being a tool used for testing with users even before the launch of the final product.