This page defines the term. The WhatsApp Channels guide covers how to create a channel, grow it and use it for a brand.
Channels live outside the chat list, in the Updates tab. Followers are invisible to each other, their phone numbers stay hidden from the admin, and the flow is strictly one-way: posts, reactions, and polls, but no replies or threads.
A channel complements rather than replaces opted-in marketing on the API: it cannot segment, personalize, or converse.