These are located on the rear end of the vehicle, facing rearward.
Taillights turn on when the headlights are turned "on". These are wired to the same switch to which the headlights are wired.
LED lights are becoming a popular choice for taillights. Halogen lights are the most common and come standard on most vehicles. Xenon lights are the third type of taillights that are strong, bright, and have a higher intensity than other lights.
These provide safety to the vehicle. It allows other drivers to appropriately gauge the size and shape of the car, while also helping to see the car in rain or snow.