A wireframe is a static, low-fidelity representation of final product. It is used as a basic guide to show all functionalities and determine what and where should appear on screen.
You may want to read about
Wireframes can easily be made on piece of paper or whiteboard, however when things get more complex and making quick changes become necessary a dedicated software may save you a lot of time.
Enhance your web or mobile design process by working on functionalities on first place.
Visually represent your product to designers and developers so they know how to follow.
Wireframes are great starting point for making prototypes - adding interactions and content is the next step in making digital product functional.