This is a general advice when working with skin meshes (even without the BGE).
One of the common issues is that you model you skin mesh but you do not look where the origin is.
Then you move/rotate/scale the whole object (in object mode) that it fits the armature.
The result might be that your mesh is still rotated 90° around some axes. As you rotated in object mode you do not see that in 3D view.
If you do <alt+R> the orientation (Object mode) will be reset and your model will look very bad.
To avoid that better apply the rotation BEFORE you rig the skin mesh.
This belongs to location. Match the origin of the armature. I recommend to keep both at the scene origin (0,0,0). That makes work much easier.
This belongs the scale as well.
Beside easier workflow, there can be other unwanted effects, if the mesh object does not have reset transformations.
Hint: the skin mesh object  and the armature (before connecting)[/edit] should have these transformations:
0.0, 0.0, 0.0
0.0, 0.0, 0.0
1.0, 1.0, 1.0
Please have a look at the guide it is described there
Pose animation is what you setup when you animate the armature in pose mode = bone animation
Motion animation is when you move/rotate/scale a complete object (e.g. the armature, not the bone) this is also called object action.
I do not know if there is an agreement how to call this things. If someone knows it would be nice to post a reference :).
Motion/rotation/scaling of an object changes the scene as all objects are part of the scene = interaction ;). This is what is usually called run, turn, jump etc…
While the pose action performs the walkcycle is an pose animation in place = the object does not move around. It just moves the arms and legs.
When you combine motion animation + pose animation it looks like the character is walking. That is the whole trick.