My article was based on the v1 rulebook as Brian writes. Unfortunately, the v2 rulebook didn't make it that much clearer, but a few of the most vague places I mention in the article has been clarified in v2.
But to sum it up:
*A vehicle is "moving" from the start to the end of its MPh - just like any other unit. This don't mean much more than the fact that only moving units can be affected by DFF.
*A vehicle is a "Moving (vehicular) Target" (C.8 of all places), if it is/has been in Motion or moved to a new hex/used VBM during that turn. If a vehicle stops, this effect lasts until the end of the AFPh. Being a Moving Target means two important things (and a few less importnat other things): It is harder to hit (case J; +2), and it is not a TEM/Hindrance.
*Motion: As Georgii2222 writes, this is only applicable outside of the MPh, and means a vehicle which is not Stopped.
*Non-Stopped: Only applicable during the MPh, but there are a few differences between Non-Stopped and Motion. The most important is that a Non-Stopped vehicle does not become a Moving Target just because it is Non-Stopped. It must also move to a new hex/use VBM first.
ex: During the enemy MPh, if your Stopped AFV passes a Motion Attempt, it becomes in Motion, and therefore immediately becomes a Moving Target which gets case J +2 To Hit DRM when the enemy attacks it.
During your MPh, if your Stopped AFV expends a start MP, it can be attacked, and is still not a Moving Target.