IP addresses in both protocols are just a sequence of bits. Combined with a subnet mask (or prefix length, the more modern term for the same concept) they divide into a network portion and a host portion. The former tells you what network the host is on, the latter uniquely identifies the host on that network. This is exactly the same for both protocols.

Or what do you mean by “parts of an IPv4 address and their meaning”?

That multicast on IPv4 isn’t used as much is irrelevant. It functions the same way in both protocols.