The 'songtaew' is the traditional bus for travel in Phuket. Translated into English as 'two rows' it is a typical example of the way the Thai language uses a simple name to describe something and this same format is used for so many things.
The songtaew has a row of wooden seats, perhaps better described as a wooden plank that runs along each side of the interior of the bus and is supplemented by a small, removable low wooden bench in the middle. Shopping and luggage can be tied to the roof or tied onto the back.
Want to try one? Stand by the roadside, that is anywhere along the road as there are no bus stops, and when you see the songtaew approaching just wave your hand and flag him down. (Please do not 'thumb' a ride, use of the thumb can be a symbol of aggression here in Thailand) The Thais will simply stick their arm out at waist level with the hand out flat and flap their hand up and down, like flapping a wing, and the songtaew will stop. Press the bell when you want to get off and walk to the front and pay the driver. Most routes will start/end at Phuket's Market in Phuket Town and you can easily find a songtaew there, waiting until the departure time.
On this note it is worth mentioning that there are also some typical body gestures that can cause confusion here. When a non Thai calls someone with their hand it can look to a Thai that you are chasing them away! It really is worth a bit of time studying body language here and avoid using hand gestures until you know the way the locals do it! And please, please remember that the use of the foot to point at something, write something in the sand, or to move something, is extremely offensive to the Thai people who believe that the foot is the lowest part of the body. In the same way it is equally offensive to step over anything, especially religious objects, food, or even to step over someone's leg.