A DHCPv4 client use the broadcast IP address to send the initial DHCP discover packet when the client is looking for a DHCP server.
A workstation will send a DHCPDISCOVER message to start the process of obtaining a valid IP address. The client does not know the addresses of DHCP servers, and that's why it sends the message via broadcast, with destination addresses of FF-FF-FF-FF-FF-FF and 255.255.255.255.