Bind pose
From TrainzOnline
The bind pose of an animated mesh is the default state of the mesh prior to any animation being applied. While there is no strict requirement on what a bind pose should look like, there are some fairly standard techniques used when modeling that lead to fairly predictable outcomes.
The bind pose is generally not displayed in-game. Wherever a mesh has a skeleton, appropriate animation(s) should be applied such that all of the bones in the skeleton have a position defined by the animation(s). There is no practical reason why the bind pose cannot be displayed, but it is usually considered an implementation detail and may not be appropriate for user viewing.