Corgi is a Welsh word from small or dwarf dog. There are 2 different breeds of Welsh Corgis: Pembroke Welsh Corgis (which originated in Pembrokeshire) and Cardigan Welsh Corgis (which originated in Cardiganshire). Both breeds come from Wales, but they are very different breeds and definitely NOT one and the same.
The Cardigan Welsh Corgi is believed to be the older of the 2 breeds. To read more about the history of the breed, please visit the following links to the Cardigan Welsh Corgi Club of America
The most noticeable differences between the 2 Corgi breeds would be that Cardigans have a full tail and they come in a wider array of colours (red or sable, brindle, tan pointed tri, brindle pointed tri-these are often called black and white, as well as blue merle with tan and brindle points). They are a herding breed, initially bred to move cattle.