Material Design Activity Indicator expresses an unspecified wait time.
Material Design FAB performs the primary, or most common, action on a screen. It appears in front of all screen content, typically as a circular shape with an icon in its center.
The Material Design Ripple component provides a radial action in the form of a visual ripple expanding outward from the user's touch. Ripple is a visual form of feedback for touch events providing users a clear signal that an element is being touched.
Material Design Bottom Navigation bars allow movement between primary destinations in an app. Tapping on a bottom navigation icon takes you directly to the associated view or refreshes the currently active view.