WebRTC uses the Session Description Protocol (SDP) to describe the parameters of peer-to-peer connections. SDP does not deliver any media itself. Instead, it is used to describe the "session profile," which represents a list of properties of the connection – that is the types of media to be exchanged (audio, video, and application data), network transports, used codecs, and their settings, bandwidth information, and other metadata.
SDP is a simple text-based protocol for describing the properties of the intended session. It provides a description of the acquired audio stream. WebRTC applications do not have to deal with SDP directly. The JavaScript Session Establishment Protocol (JSEP) abstracts all the inner workings of SDP behind a few simple method calls on the RTCPeerConnection object.