Yepp, /dev/null is the neverending garbage can
"chmod +x run_game" this means make run_game executable, if you didn't you'd have to run it like "bash run_game" (substitute bash with your shell
./run_game > /dev/null 2>&1 &
This means to execute run_game, redirect stdout (standard out) to /dev/null, then bond together stderr (standard error output) and stdout.
The & at the end just says this program should run in the background.
There's an easier way then doing it like that thou. This will do the same thing. I'm not even sure if redirecting and then bonding works.
Anyway, this tells the shell to redirect both stderr (standard error, the "2") and stdout (standard out, the "1") to /dev/null
./run_game 2>&1 /dev/null &