Multicast, Broadcast.. how do they understand it?

Hello everyone, I am learning about networking, and I understood the Unicast, Multicast and Broadcast methods, but one thing that I just can't understand is how a router or switch knows how to deal with IP addresses. Given the network 192.168.56.0/24, the broadcast is 192.168.56.255, but how does the router know this address is for broadcast, the message will be transferred to all the computers in the network. How does it understand that? Is it inside the IOS of the router? or some flag inside the IP Packet? or a Standard implemented inside the router? Thank you