The story of the Targa in the 911 range started in 1967. It was originally conceived to have a 911 Cabriolet that was in accordance with the US regulations that did not allow full convertible models. Things have changed now, but the Targa is still here and it's perfectly bridging the gap between coupes and convertibles.
But things weren't always that easy. The concept of the Targa has always been about having an aluminum-finished bar that goes over the car to protect its occupants. Things changed in 1993 with the 993. Porsche introduced a revised mechanism of the roof. Instead of having a removable panel, the Targa was now equipped with a large glass that slid back to create an open space above the cabin. The true essence was gone but the name stayed. The automated mechanism was actually way more practical than the manually removable panel. This system went on for nearly 20 years up until the 991, for which Porsche decided to reintroduce the famous bar to give it a retro style.