Flexbox, short for Flexible Box Layout, is a CSS layout model that makes it easier to design responsive web pages. It allows developers to arrange items in a container, either in rows or columns, and control their alignment, spacing, and size. This flexibility helps create layouts that adapt to different screen sizes without needing complex calculations. With Flexbox, you can easily center elements, distribute space evenly, and reorder items without changing the HTML structure. It simplifies the process of building layouts, making it a popular choice for modern web design. Overall, Flexbox enhances the way we create and manage layouts on the web.