Unicast, Broadcast & Multicast are the three type of communication in computer network which the devices does in a network.
In unicast the devices communicate as one to one. It means a device sends data or message to only one device separately. Other devices are not joined or informed by the data process by which they stay disturbance free.
In Broadcast the device communicates as One to all. It means when a device send a information one device, all other device in the network also get informed about it.
In multi cast the communication of sending information does one to all. It means a device can send or receive multiple informations at a time.