The traffic lights is a classic exercise project in learning microcontrollers. In its basic form, it is formed with some wires, 3 LEDs and matching current limiting resistors and build unto a breadboard or PCB. While it may not be difficult to build, the time and resources spend may sometimes be enough reason to look for off the shelve solutions.
The 3-LED module aka the “Traffic Lights Module” is basically 3 Leds with the necessary resistors and a common ground pin (CC) built into a small PCB with the 3 signals and CC pin broken out into 4 standard pitched right-angled headers. This makes it easy to connect to an existing circuit or an Arduino and also allows connection in a breadboard. It may also be used as simple notification module.
The module could be directly inserted into the GND-13-12-11 pins of the Arduino/Saleng Uno shown below: