A wireframe is a black and white version of your website that is designed to prove the functionality and features as they will work in the browser. No design elements are applied at this stage as the prototype is just built to allow all parties to make final decisions on the functionality. Here is an example of a wireframe: http://prototypes.thewpdevshop.com/proctormajor/
These wireframes can be connected together through hyperlinks to show a complete flow of the website or app. This allows the users to navigate through different pages or screens of the website.