A broadcast address is a special type of network address used to send data to all devices within a specific subnet. It allows a single message to be transmitted to multiple devices simultaneously, rather than sending individual messages to each device. This is particularly useful in local area networks (LANs) where devices need to communicate efficiently. In an IPv4 network, the broadcast address is typically the highest address in a subnet. For example, in the subnet 192.168.1.0/24, the broadcast address would be 192.168.1.255. When a device sends data to this address, all devices on that subnet receive the message, facilitating quick communication and resource sharing.