Hi Lara - when doing a surface blend the curves that actually are blended between are not just simple curves but rather _edges_ of surfaces.

An edge is kind of like a marker that marks boundaries of surfaces - you cannot just grab an edge and edit it directly. But if you want to resize the entire surface, the edge will get resized along with it and you can have a Blend update after that kind of edit. Similarly you can't move just one edge itself but if you move the surface the edge which is part of the surface will move along with it and the blend connecting to the edge will also move unless you have done other operations onto the blend itself.

- Michael