I'll spare repeating the detailed history of the car and go over it as quickly as possible.

The first generation Golf, or Mk1 - Mark 1 - was released in 1974 and was to replace the aged VW Beetle. The Golf (the name had nothing to do with the sport but is the German spelling of Gulf, as in Gulf Stream) differed very much to the Beetle mechanically as well as aesthetically, moving from a rear-mounted air-cooled engine to a front mounted liquid-cooled engine, but was to meant to achieve the same goal: a small, affordable car.

Several variations of the base 2 and 4 door cars were made, as follows.

GTI

The Golf was never meant to be fast, let alone a sports car. As a kind of gimmick, engineers at the Volkswagen factory fitted a light little Golf with a Bosch mechanical fuel injection unit, usually reserved for sports and upmarket cars. VW execs were cautious of the idea and only intended to sell the quick GTI in Germany, but demand from other countries, particularly the UK influenced VW to take production seriously. Thus the concept of the 'hot hatch' was born.

GTIs feature either a 1.6 or 1.8lt mechnical injected SOHC engine. GTI stands for Grand Touring Injected.

Cabriolet or Cabrio

The Cabriolet is simply the convertible version of the Golf. These cars were actually not built by VW, but were built by the independent car factory Karmann (known for the Karmann Ghia, which actually uses many components from the Beetle). As a result, the Karmann factory kept making Mk1 Cabriolets well passed when Volkswagen themselves ceased production. That's why it's possible to buy car made in 1993 closely resembling the same model first made in 1974. Late model Cabriolets were fitted with modern body kits, the 1.8lt injected GTI engine and different, newer interiors in an effort to give the aging car a more modern look.

All Cabriolets came from the Karmann factory.

Diesel

Diesel Mk1s were first manufactured in 1976. Performance wise, hese cars were very comparible to smaller petrol engined Mk1s. Many engine components are shared between both diesel and petrol models.

Rabbit and Caribe

The Volkswagen Rabbit and Caribe were the local names given to the Golf in the USA and Mexico, respectfully. They are essentially the same car as their European counterparts, though some later models had square headlights. The Rabbit name was later dropped.

Citi Golf

Citi Golfs were made in South Africa between 1984 and 2009. They are, fundamentally, Mk1 Golfs but with some subtle changes, including a slightly sloping front grill, different C pillar design, integrated rear window whiper. The most significant change was the installation of a Skoda dashboard in 2004.