The MediaStreamTrack.onoverconstrained event handler is a property called when the overconstrained event is received. Such an event is sent when the track is again able to send data.
The MediaStreamTrack.remote read-only property allows Javascript to know whether a WebRTC MediaStreamTrack is from a remote source or a local one. It returns a Boolean with a value of true if the track is sourced remotely (that is, sourced by an RTCPeerConnection), or false if it is sourced locally.
A MessageEvent is the interface representing a message received by a target, being a WebSocket or a WebRTC RTCDataChannel
The RTCIceServer dictionary defines how to connect to a single ICE server (such as a STUN or TURN server). It includes both the URL and the necessary credentials, if any, to connect to the server.