Servos: attach() and write() Arduino newbie here, so this question might sound too simple. I am trying to run a parallax continuous rotation servo using Arduino Uno. From the reference, I learned that the servo needs to be "attached" to one of digital pins with PWM capability, and the servo's speed can be controlled by write(0~180, 90=stop).

But I am having a hard time understanding the role of the PWM digital pin. If the servo's speed and direction of rotation is determined by write(), what is the role of attach(pin#)?

Thanks in advance!
attach tells the servo library which pin it should be writing to, this is stored somewhere in ram and write will look it up and communicate with the correct pin. 

It's possible that you are using the other pwm capable pins for other purposes and suddenly having that library interfere with that is not a good thing.