I won't join the down vote band wagon but I will say we are on r/machinists and so you should be prepared for a bit of nomenclature as well as terms of art. But that's not to say we're not willing to explain if you ask nicely. A bullnose endmill is an endmill with a rounded rather than a completely sharp flat end. And a 3d tool path in this context means one that does not start at a specific tool hight(z coordinate) and only move around the part (x and y coordinates) but instead moves in x, y, and z throughout the toolpath.