GeoLock is built in into Cast to comply with some licensing issues for music. Some licensing agencies ask to block access in countries where they have no rights to play the music. Cast can be configured to only allow certain countries to tune in to your stream.
Deny- vs Allowlisting
Cast has two options a denylist and a allowlist. The allowlist option allows only certain countries to tune in. All others including non-identifiable will not have access to the stream. A denylist does the exact opposite, this will ban certain countries but allow non-identifiable IPs. In case you use a allowlist you can also select to allow IPs which we can not identify.