If a Macbook is asleep, it will just wake up, you'll see the keyboard light, there is no need to press the power button.
If there is a need to press the power button it is because the machine is off. Don't worry, it will make a distinctive and iconic sound once it is not off and display, you guessed it, a white apple logo on the screen.
What circumstances lead to your confusion about its state? I can't relate!