Wireframing is a practice used by UX designers which allows them to define and plan the information hierarchy of their design for a website, app, or product. This process focuses on how the designer or client wants the user to process information on a site, based on the user research already performed by the UX design team.
When designing for the screen you need to know where all the information is going to go in plain black and white diagrams before building anything with code. Wireframing is also a great way of getting to know how a user interacts with your interface, through the positioning of buttons and menus on the diagrams.

Without the distractions of colors, typeface choices or text, wireframing lets you plan the layout and interaction of your interface. A commonly-used argument for wireframing is that if a user doesn’t know where to go on a plain hand-drawn diagram of your site page, then it is irrelevant what colors or fancy text eventually get used. A button or call to action needs to be clear to the user even it’s not brightly colored and flashing.