Axure does most of what the current breed popular wireframe tools do (Sketch, etc.), and more. Axure comes with a very powerful action / prototyping engine that allows you to string together animations and other hard-to-describe interactions that are difficult to show or describe in other ways. Axure also has a very strong templating / "objects" aspect where you can easily drop objects within objects, and editing the template of the object affects every instance of that object. This makes Axure useful for creating modular designs and wireframe languages for a suite of features across your app. Lastly, Axure is great in sharing products to customers, as you can upload your work to a private, passworded link (for free, no less) to be shared with clients. This is invaluable for delivering work.

I use Axure RP to build lightweight interactive UX prototypes for usability tests. It does a great job of getting input from forms and making it possible to store, manipulate, and use the data throughout the prototype, which makes simulations for usability tests more realistic. And Dynamic Panels make it possible to build convincing simulations of single-page web applications.

The interaction tools provided by this software allows designers to create functionality for their prototypes unlike anything that is available elsewhere. By allowing designers more than just the ability to create static images, as was the old style with Photoshop, we are able to take on more of the developer role without knowing how to code and ultimately gain more control over our designs.