A broadcast message is sent from a specific node to all other nodes in its broadcast domain.
Ethernet is a layer two protocol that uses broadcasts. Ethernet broadcasts are directed to the destination MAC address of FF:FF:FF:FF:FF:FF.
IPv4 also supports broadcasts at the network layer. The IPv4 broadcast address varies with each subnet. For any given subnet, the last address in the block will be the broadcast address. For example, in the IPv4 address range of 192.168.30.0/24, the last address, 192.168.30.255 is reserved for broadcast.