These terms refer to the delivery of video images from the source to the destination using Internet Protocol (IP) technology. 

Uni-cast refers to one destination per delivery.  If there are multiple destinations, the source has to repeat the delivery for each destination. 

Broadcast refers to one source and delivery to all destinations on the network. 

Multi-cast refers to one source and pre-defined multiple destinations of the network.  Obviously, multi-cast is the most efficient or desirable form of delivery.