Prototyping vs Wireframing
From our experience these two notions are often confused and many of our clients do not see the difference between plain wireframing and building full-scale prototypes.
Wireframes are used as part of documentation for the project, these are the images, which show how the content of the future app is laid out and structured. Prototypes on the other hand let you interact with the screen, e.g. press some buttons, see dynamic elements, etc. This is a close-to-life simulation. Of course it will be different from a final product, but it gives an all-encompassing vision of its function set and capabilities.
Although prototyping is more complex, time-consuming, and requires sufficient spending, it allows companies to sufficiently cut down the cost for future development and reduce the programming effort.