How do you check for a certain phgrase from the serial monitor?

How do you check for a certain phrase or a string or letters or words from the serial monitor? I want to be able to type "turn on" and "turn off" to turn on and off an led. So far if there is any input available, the led ill turn on. I want it to only turn on if there is a command. Thanks!

So far if there is any input available, the led ill turn on. I want it to only turn on if there is a command. Thanks!

See Robin2's tutorial: http://forum.arduino.cc/index.php?topic=396450.0

You could make life easy and just send '0' for off, and '1' for on.
But if you are more interested in string parsing, send: "I would now like my LED to turn ON, pretty please, with sugar on it."