Unicast
In plain terms
One-to-one communication between a single sender and receiver.
Going deeper
Unicast sends data from one source to one specific destination, the most common form of network communication. Each packet has a single recipient.
Under the hood
Contrasts with broadcast/multicast; the default for typical client-server traffic.
Examples
Web browsing, file downloads, typical client-server traffic, direct messaging.
Think of it like...
Like a private phone call to one specific person.