In an individually Addressable LED strip, the LEDs each have a companion IC to give them independence and intelligence. In most Adafruit Neopixel products, this IC is embedded directly into the LED package. The finished product has the same four-pin package as most RGB LEDs, but instead of RGB+, these four pins are power, ground, data in, and data out. The “data out” feature is what allows the modules to be connected end to end in a strip or ring. The modules communicate using a single wire that is extremely dependent on timing. Real time processors like the Arduino handle this well, while a microprocessor like the core of a Raspberry Pi requires quite a bit of additional programming to accurately drive smart LEDs.