unicast

Unicast is peer-to-peer. One sender and one receiver. The world wide web is built on unicasting, so is email exchange. Most unicasting is done via TCP, but isn't restricted to this.

Contrast this with broadcasting which has one source that "feeds" multiple receivers at the same time (usually on the same LAN).

Similarely multicasting does the same but allows the receiver to "opt-in". Multicasting is designed to be routed and was historically not popular because of the CPU it took up for no charge of the sender. There is a certain turn-around point though when it is costlier to harbour unicast traffic than multicast.