The targa is a car with a removable roof. Similar to a convertible, but different in the fact that only the very top part of the roof is is removable, (the section over the door only). The rear window, and a small section of roof still remain. This remaining section is often strengthened to roll bar stiffness, (so it can support the car in the event of a roll over).
Porsche has produced more cars with the targa top than any other manufacturer. Although Honda, Toyota, and many of the higher end performance automakers have also made targa models.