Sorry for my trivial question. I'm a newbie and I'm walking through a cave tutorial. I can deform a mesh with a NURBS curve but I can't further edit the deformation through manipulating the curve after applying the modifier. Pressing Apply on the modifier 'freezes' the effect and the modifier icon in the object tree disappears (is that a standard behaviour?). Moreover, when the mouse pointer is over the Apply or Apply as Shape buttons, I read the same tip: 'Apply modifier and remove from the stack'. Is that a bug? My configuration is Blender 2.72b on Ubuntu 12.04 LTS (64 bit).
EDIT: I can edit the deformation before the modifier is applied. I expected a further deformation editing through the curve manipulating because I am too influenced by CATIA :)