Take the definition, read
WebRTC is a free, open project that provides browsers and mobile applications with Real-Time Communications (RTC) capabilities via simple APIs. The WebRTC components have been optimized to best serve this purpose.
communication in real time between browsers or mobile phone, i.e. communication between clients.
This is not restricted to data through data channel to send everything, files, data streams bypassing the server.
As an example - did service joint drawing. The coordinates of the cursor of the user sends to another user.
Can files to fumble.
Only to find each other clients will still need some common point. managing the server.