Yep. A Template is where you start. It can be altered in any way you desire.
A skin is the finished product, it can't be altered afterwards, only painted over.
A little explanation: take a look at the screenshot below (click). That's a template.
On the right side you can see part of the many layers used in that template.
The US insignia has been marked and could be altered now. You could simply delete it,
repaint it, replace with some other insignia, or create a new layer for new markings of your choice.
After you're finished (and saved your template to a format which supports layers, e.g. .psd, .psp., .cpt.),
you'd combine all the layers into one and save it to the skin's format, .bmp (and convert it to 8-bit format,
but that' another story...)
This is irreversible; once you saved the Bitmap, it becomes "one piece".
That's the main difference between skin and template.