Definition of Broadcast Packet from Network Encyclopedia.
A broadcast packet is sent over the network of computers and picked up by all hosts on the local subnet. Broadcast packets can also be forwarded to other subnets if routers are configured to forward IP broadcasts, though this is not usually the case.
In other words, when a computer tries to connect to a network it sends out broadcast packets. Broadcast packets have no specific destination address. Instead, the broadcast packets are meant for all computers on the network. A connecting computer sends those packets to inform all the other computers on the network that it is about to become part of the network. These broadcast packets will switch forward to all computers behind them.
Broadcast packets is a way to get attention
When a new computer connects to the network it has to let the other computers know its there. The new computer has no idea of what other computers that are already there. The computers already on the network have no way of telling there is a new computer connected to the network. The new computer, therefore, sends out several broadcast packets.