Next we have the ICE lines, which is the mechanism chosen for NAT traversal in WebRTC. You can find a very didactic and comprehensive explanation of ICE here. ICE is complex enough to deserve its own post, but I will try to explain its SDP lines in an understandable way.
Once the ICE candidates are exchanged, a verification process starts where both browsers try to reach each other using the candidates provided. The ice-ufgra and ice-pwd credentials are used in that process to avoid receiving potentials attacks from endpoints that are not involved in the session who could potentially create a media session without authorization.