The F11 key, commonly found on computer keyboards, is used to toggle fullscreen mode in various applications and web browsers. When activated, it expands the current window to fill the entire screen, hiding the taskbar and other interface elements. This feature is particularly useful for presentations, gaming, and watching videos, as it provides an immersive experience without distractions. In most web browsers, pressing F11 again will exit fullscreen mode, returning the display to its original size. This functionality is supported by popular browsers like Google Chrome, Mozilla Firefox, and Microsoft Edge, making it a widely recognized shortcut for users.