The read-only property RTCPeerConnection.remoteDescription returns a RTCSessionDescription describing the session (which includes configuration and media information) for the remote end of the connection. If this hasn't been set yet, this is null.
The returned value typically reflects a remote description which has been received over the signaling server (as either an offer or an answer) and then put into effect by your code calling RTCPeerConnection.setRemoteDescription() in response.
const sessionDescription = peerConnection.remoteDescription
On a more fundamental level, the returned value is the value of RTCPeerConnection.pendingRemoteDescription if that property isn't null; otherwise, the value of RTCPeerConnection.currentRemoteDescription is returned. See Pending and current descriptions in the WebRTC Connectivity page for details on this algorithm and why it's used.
This example looks at the remoteDescription and displays an alert containing the RTCSessionDescription object's type and sdp fields.
const pc = new RTCPeerConnection();
const sd = pc.remoteDescription;
if (sd) {
alert(`Remote session: type='${sd.type}'; sdp description='${sd.sdp}'`);
} else {
alert("No remote session yet.");
}