They aren't part of the design process, but of the planning process. Wireframes use simple, sketch-like elements to show the basics of a website.
Design for small and large screens with fast wireframing and mockup tools. It’s no longer enough to design for one device or screen. Use Adobe XD to create designs that look great on desktop, tablets, iPhones, Android devices, and more. Save time with UI kits that contain templates, components, and common design features optimized for different screen sizes and devices.
When Creating a Web Site, The Goal is to Create a Design (noun) a specification of an object, manifested by an agent, intended to accomplish goals, in a particular environment, using a set of primitive components, satisfying a set of requirements, subject to constraints; (verb, transitive) to create a design, in an environment (where the designer operates)
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.