A BroadcastReceiver is a component in the Android operating system that allows applications to listen for and respond to system-wide broadcast messages. These broadcasts can originate from the system or other applications, notifying the app about events such as incoming calls, battery status changes, or network connectivity updates. When a broadcast message is received, the BroadcastReceiver executes a specific piece of code defined by the developer. This enables apps to perform actions in response to these events, enhancing user experience and functionality. Developers can register receivers in the app's manifest or dynamically within the code.