The three icons may represent data centers, groups of devices or a unique device - customizable by the user. Several backgrounds (this rear "layer" is static) are offered out-of-the-box, or user-defined backgrounds can be substituted. The icons* will flash when one or more alarm conditions within the center, a group of devices or a single device crosses a defined threshold. In most cases a drill-down capability is offered, providing quick visibility into the room, rack or device within the Aperture UI.
*each is a floating front "layer", appearing along the bottom of the screen at time of configuration. The icons are drag-n-drop, placed by the user against the background.