A "bushcraft" knife is one that would excel at woodworking, carving, etc. Not so much a hunting, tactical or survival knife, rather more of a bush tool.. A bush tool in the same manner of a camp ax or hatchet. Most modern bushcraft knives are inspired by working knives from Scandinavia: Swedish Mora knives, Finnish puukkos, Sami leukus, and Norwegian tolleknivs. These knives have scandi grind blades which are well suited for carving and general woodwork and you will see this type of grind on many modern bushcraft knives, although flat ground blades are also preferred by many. Also, modern bushcraft knives tend to have thicker blades and full tang handles which can handle batoning better than their traditional Scandinavian counterparts.
That said, what works for one person may not work for another, so like drillsgt71 stated, one person's idea of an ideal bushcraft knife will differ from another's. For some, a simple $10 Mora will do everything one could ever need out of a bushcraft knife while others may want something more robust. Some people like scandi grind blades, some do not. Some can get by with a sub 4-inch blade, some may want something larger. It all depends. In effect a bushcraft knife can be anything and everything from a traditional puukko to a modern camp knife that will aid you in handcarving, preparing kindling, foraging, etc..
To get a good idea of what "bushcraft" knives are like take a look at a few knives like the Spyderco Bushcraft, Mike Lummio's BCNW-O1, Ray Mears' Woodlore, the BHK Bushcrafter, the Condor Bushlore, the Helle Eggen, the Helle Tamegami, the Mora Classic, the Mora Clipper, etc..
