This is the 24 LED NeoPixel Ring from Adafruit, a small chainable 2.6" (66mm) outer diameter board equipped with 5050 WS2812 RGB LEDs. The WS2812s are each addressable as the driver chip is located inside the LED. Each NeoPixel Stick has ~18mA constant current drive so the color will be very consistent even if the voltage varies, and requires 5V.
Every ring is equipped with a single data line with a very timing-specific protocol requiring a real-time microconroller with a 8MHz or faster processor such as an AVR, Arduino, PIC, mbed, etc. There are solder pads on the back for connecting wires or breadboard pins and two mounting holes for securing this board to many different surfaces.