Internet Protocol multicast groups are a method used to send data from one source to multiple destinations simultaneously. Instead of sending individual copies of the same data to each recipient, multicast allows the sender to transmit a single stream of data that can be received by all members of the group. This is efficient for applications like video streaming or online gaming, where the same content is delivered to many users at once. Each multicast group is identified by a unique IP address in the range reserved for multicast, typically from 224.0.0.0 to 239.255.255.255. Devices that want to receive the multicast data join the group by subscribing to this address. This way, they can receive the data without needing to establish a direct connection with the sender, reducing network congestion and improving performance.