The Start Menu in Windows 10 replaces the Start Screen from Windows 8 and acts as a navigation hub containing frequently used apps, shortcuts, and live tiles that display real-time updates. It provides access to File Explorer, Settings, Power options, and an alphabetical list of all installed apps. The Start Menu can be customized by rearranging tiles, creating groups, resizing tiles and the Start Menu itself, turning off live updates, and pinning/unpinning apps.