WHIP stands for WebRTC-HTTP Ingestion Protocol.
WHIP enables connecting browser based users and live inputs directly to streaming services.
It is an IETF draft specification (here), which adds a simple signaling layer on top of WebRTC that can be used to connect a WebRTC publisher to a WebRTC media server – usually streaming services and/or CDNs.
The publisher in this case only sends media and doesn’t receive media.
Since WebRTC doesn’t include its own signaling protocol, WHIP has been proposed, for solving a very specific market need – in the streaming industry, there is a clear decoupling between the various network components – publishers, media servers and players. Each application or service provider can mix and match these three entities as he sees fit.
For WebRTC to fit into the streaming industry, such decoupling was needed, and as a result, there was a need for a clear signaling protocol to connect the publisher to the media server, which is what WHIP does.
See also WHEP