The GF-27 is a specialist knife blade for butchering raw meat. The curved thin blade is designed to slice through joints in raw carcasses. The shape of the knife with its right angle curve in the blade is made to slash across flesh and so separate the meat from bones, ligaments and other parts that are not wanted. It is a specialist knife and does not work well for cutting or chopping vegetables and other regular kitchen work. The GF-27 has a bolster, which gives it an edge over the bolster-less G-28. This is particularly useful when the slime from raw meat can make the knife handle slipped, just having the bolster there gives you a little more drip, control and confidence when using the knife.
The butcher knife shape comes from a very old design. In the wild these knives were used for a huge variety of tasks, for cutting up food, skinning animals and self defense.