CS:GO is a game about tight teamwork.
Grenade binds bind grenades smokes, molotovs, flashbangs, etc to keys on your keyboard.
There should be a video up on YouTube covering all the corners of the entire map list.
This way, when your teammate asks for a flash so he can push through that smoke on Cobble B Long and get himself killed, you can at least accommodate his wishes without cycling through your grenades like an unorganized anarchist.
Switching to your knife also increases your movement speed, and it can come in handy if you also get tagged in the process.
Editor's note: if you put shadows on high you will see shadows when you're further away, giving you an advantage.