Before you design a website, you need to come up with a plan. This is the way you want your site to look like on paper. Wireframing is how you design your site at the structure level.
A wireframe is what you use as a layout of your website. Consider it like a design of a house. You use the wireframe to create a layout of the content and functionality of the on the page. It takes into account user needs and online journeys.
Wireframes come at the early stages of the web development process. It is a structure of the page written on a page before adding visual design and content.