An RGB LED isn't exactly a single light emitting diode. It's more like three rolled into one, or maybe it's a three-headed diode. You can see the three semiconductor light sources inside. Using one of these with a microcontroller requires three current limiting resistors, plus three free pins capable of pulse width modulation. Of course, this is the old-fashioned way of doing things. Digitally 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 a little buddy.