Here's a shot at describing them. Again, this may have an ATSC slant. Callsigns are global names for Broadcasters. Network names are generally unique within a country but not across countries.
Broadcasters can be either independents, or local affiliates of a network.
Channel names are those names that appear in EPG's. They are assigned by the transport company carrying the guide, and are unique only within that transport company. However, the Channel that is called HBO in one Transport may well not be the same Content as the Channel that is called HBO in some other Transport. HBO has multiple feeds that the Transport Companies may or may not choose to carry. However, they are in a well-managed namespace.