 An RGB LED isn't exactly a single light emitting diode, it's more like 3 rolled into 1, or maybe it's a 3 headed diode. You can see the 3 semiconductor light sources inside. Using one of these with a microcontroller requires 3 current limiting resistors, plus 3 free pins capable of pulse width modulation. Of course this is the old fashioned way of doing things. Only controlled LEDs make RGB lighting much easier. Each one of these has a built-in driver chip that listens for color data on its serial port. And when that properly formatted message arrives, this little NeoPixel kicks into gear and handles all the PWM and color control on its own. And continues to do so until it's told otherwise. Thanks little buddy.