I recently purchased CO: BFTB, and wow – amazing and overwhelming! I'm also a noob to military strategy, so there's a lot for me to learn.
I've immersed myself in the great assets available for the game and its predecessors, having read the manual, worked through the tutorial scenario with the videos (twice), and read through Markshot's mini-guides, tips, and battle planning checklist (whew).
I plan to try playing a short scenario or two tonight – I think I've reached the knowledge saturation point and now need to gain wisdom that only comes from playing (I did finish out the tutorial on my own). However, I have a couple of questions from my preparation that I'm hoping to clear up.
I am a bit confused regarding the use of direct fire units. For example, here is an excerpt from Markshot's COTA guide:
Yellow - All our direct fire guns will be concentrated on hill over looking the Bridges and
Tempe. They will break enemy positions near the bridges and prevent reinforcements.
We'll also place a few guns to cover the Pz 3 Regt.
Are these simply any unit that shows up with the “Guns” unit filter employed that are NOT bombarding arty?
I am coming into this pretty naïve regarding military armaments, so the terminology can be a bit confusing. Are these things like machine gun nests, anti-tank guns, and bazookas, etc? I am trying to take some time on the equipment tab to study the composition of units and double-click on stuff to read more about it

Next, is it typical to give these units independent orders, and do you use a “Defend” order with “in situ” formation? What about the “Fire” command? Is that independent of a defend order, replace it, or...how exactly is it used?
I understand the use of fire bases for arty, and factors regarding attaching/detaching mortar units, but the direct fire guns are still a bit of a mystery!
Thanks!
Scott