OK, enough with abstractions, let's see under our belated hood, how WebRTC is implemented by FreeSWITCH.
FreeSWITCH is a complete WebRTC platform, and can act as both WebRTC gateway and WebRTC Application Server. Eg, FreeSWITCH is able to connect WebRTC clients to external "normal" SIP and PSTN services (or PBXes), enabling already existing or legacy services to be accessed by one billion browsers.
At the same time (and this can be literally true: while acting as gateway for some external services) FreeSWITCH is able to directly serve to WebRTC clients (browsers and apps) the exact same audio/video applications is serving to "normal" SIP and PSTN clients, such as PBX, IVR, Call Center, Conferencing System, Calling Card, etc applications.
To FreeSWITCH, WebRTC is just another kind of communication channel, along with SIP, TDM, MGCP...