A Broadcast Receiver is a component in mobile devices that allows them to receive and process broadcast messages, such as radio signals or notifications. It listens for specific intents, which are messages sent by the system or other applications, and can trigger actions in response. This makes it essential for features like receiving SMS messages or alerts. In the context of Android development, a Broadcast Receiver is implemented as a subclass of the BroadcastReceiver class. Developers register these receivers in the app's manifest or at runtime, enabling them to respond to various system-wide events, such as changes in network connectivity or battery status.