title: What does CPU frequency represent in an Arduino board?
body: <p>I'm new to Arduino and microcontrollers. </p>
  
  <p>I was studying the specs and found that even the same board may have different frequencies with different input voltages (3.3V vs 5V). So the question is, what does frequency represent? Does it represent how many lines of assembly code it's able to run? Or the maximum PWM frequencies it's able to output? </p>
  
  <p>A further question would be, if I'm looking for a board for a specific project, how do I decide which frequency I will need a priori, instead of trying everything out and see which one works? </p>
  
  <p>What makes me more confused is that when it comes to computer CPUs, it seems that lower frequency CPUs can actually run faster than higher frequency ones (e.g. Intel). So how do I actually know how fast a microcontroller can run? </p>