A forkbomb is a denial of service bash command that blocks the server, duo to high cpu load.
The script is creating a recursive function and is infinitly launching itself - so the system will be blocked.
Usefull for testing vHosts which are sharing ressources if high load is affecting other hosts.
(Thats the only thing that i could figure out what you can do usefull with this script.)
Here is a forkbomb example.
Better dont execute it in shell :D
:(){ :|:& };: