What does this linux command mean "route add -net 224.0.0.0 netmask 240.0.0.0 eth0"

Could somebody explain what exactly this command means in relation to transmitting and receiving multicast traffic

route add -net 224.0.0.0 netmask 240.0.0.0 eth0

The "224.0.0.0" is a reserved range of IPv4 addresses having special multicast meaning (IPv4 Multicast).

The command in itself just means that the multicast routing should go through the "eth0" interface.

It was probably intended to mean "send all multicast through eth0", however 224.0.0.0 is not the correct netmask for multicast. The correct netmask for multicast would have been 240.0.0.0. This command specifies all addresses between 224.0.0.0 and 255.255.255.255, however the multicast range is really only 224.0.0.0 through 239.255.255.255. The rest of the range specified here is the "Class E" addresses, which are "reserved for future/experimental use". Its unlikely that these addresses are being used, so there is probably no difference.