A floating action button (FAB) expandable menu is a button placed at the bottom-right corner of an app screen, typically shown as a circular icon. When tapped, the FAB expands to reveal additional options. The expandable FAB is particularly useful for saving screen space and reducing clutter, helping to create a cleaner user interface. It allows users to access important actions quickly while also offering extra choices when needed.^[1]

FABs are a feature defined in Material Design and are commonly used in Android apps. While you may encounter similar buttons on iOS, there is no official mention of them in iOS Human Interface Guidelines. FABs are an effective way to keep the focus on key tasks while providing users with easy access to secondary actions.