is a bundle of network protocol standards (e.g. application layer/network-level API/web service) that enables peer-to-peer/real-time communication without a mediator server
faster than traditional peer-server-peer communication
BUT still needs at least 2 servers to help initiate the peer-to-peer connection:
- STUN Server to provide client ice-candidates (i.e. their own public IP address port tuples)
- Signaling Server - for 2 clients to exchange Session Description Protocol (SDP), which contains ice-candidates and other metadata
- TURN Server needed only when client is behind a Symmetric NAT and/or Firewalls - Bastion Host
see also: Real-Time Transport Protocol (RTP) & Real-Time Transport Control Protocol (RTCP)

in depth overview, but code not up to date: https://hpbn.co/webrtc/

WebRTC - Pros & Cons

Pros	p2p allows low latency for high bandwidth content standardized API
Cons	maintaining STUN and TURN servers p2p falls apart in case of multiple peers (discord case)

Web Real-Time Communication (WebRTC)