GMC is not a company in itself, but a division of General Motors in the United States. It is focused on producing commercial and pickup trucks as well as a large variety of utility vehicle. It also manufactured vehicles for military purposes. The GMC production is meant for markets in North America and in the Middle East.
The history of GMC starts together with the one of GM which was founded in 1908. However, the first trucks under the GMC brand were only launched four years later at a famous auto show in New York. In time, GMC evolved and became a division of the giant automaker. It turned out to be very profitable and the sales of GMC often helped GM throughout its history. The most recent example is in 2009 when GM was able to avoid bankruptcy thanks to GMC.
As said, the current GMC portfolio only includes trucks of light or medium size, pickup trucks and SUVs. This was not always the case because in the numerous years since it was founded, the division used to also handle heavy trucks, vehicles for military use, sanitary vehicles, fire trucks and buses.
GMC trucks are a lot like Chevrolet trucks except for the plates and the grills. GM had to juggle with both brands in order to keep them both profitable. This is why Chevrolet trucks were not available elsewhere than in authorized dealerships. GMC trucks, on the other hand, were available in other dealerships also. They were sold together with Cadillac and Buick vehicles. This was a very smart move because it didn’t put Chevrolet and GMC in direct competition, but it allowed Buick and Cadillac to offer more than just cars. In 1996 GMC merged with Pontiac. This allowed the former one to present an increased lineup of vehicles. Throughout their history, GMC trucks were always marketed as being superior to Chevrolet ones. They were presented as a better alternative to Chevrolet trucks and this made them very profitable. The Pontiac brand is no longer manufactured nowadays, but GMC trucks are still sold in North America through Buick and Cadillac dealerships.
GMC was always a profitable division for General Motors and it is unlikely that it will be discontinued any time soon.