Question : Why Ping is blocked by my FW (ICMP) and not fping ?

Hello Team,
I've tested ping vs ping on a host witch the ICMP/IP address is blocked by my FW.
With ping the result is "no response...", of course it's blocked.
With fping the result is OK !
Can you tell me what is the real difference between ping and fping (about protocol, port or other...) ?
How can I protect my hosts from fping request ?
Thanks,
Eric 