When cooking on a BBQ with wood chunks, do you still need charcoal to get the BBQ a light or can you use just the wood chunks/chips?

You can just use wood, and prepare it as you would a small campfire. Add the meat when embers form.

Typically you are cooking on coals and using the wood to flavor the smoke, although I know some bbq ers who will burn down oak to coals and use that. Be sure to remove the oak bark, which makes your bbq bitter.

Regardless of whether you mean just a grill or an actual BBQ/smoker, meant to cook low and slow, yes you need the charcoal. I personally prefer lump charcoal, made of oak or mesquite are options, but charcoal briquettes (NOT Match-Light) are fine too. Avoid Match-Light because when you BBQ low and slow and keep adding briquettes as the hours go by, you don't want the byproducts of the outer lighter fluid layer to end up on your food. If you just grill with Match-Light briquettes, meaning you will not have to add extra coals later, you're supposed to wait until all of that stuff burns off and the coals are glowing white hot before you cook your food. I prefer to just use non-Match-Light charcoal and I light it in a chimney.

Basically charcoal provides the long, sustained release of heat needed to keep your BBQ at the desired temperature as you cook. It also is a great source of heat to keep your soaked chips smoking. Since they are wet, they will have a tendency to go out unless they are on top of a good heat source like charcoal.

If you try to just light the hardwood chunks on fire and use that as the sole heat source, it won't be as sustained and steady as the charcoal. Also, they say that using dry chips/chunks leads to a harsher flavor, whereas wet chips and chunks will provide a mellower smoke flavor.

Good luck with your BBQ!

What Bill said for charcoal grille, if you want to buy a gas grill you could get a smoker pan to impart the smoked flavor (Amazon and pretty cheap). Much less clean-up and general wait times to start grilling.....meaning you will want too grill more often.  If  you go charcoal look into a smoker grill (offset), so if you ever decide you want to go low and slow for many hours (pulled pork, ribs, brisket) you could do that with great success.

We used to always use wood that we'd cut ourselves and allowed to dry out. I used either barbecue fire lighters or lighter fluid to get the wood going - same as for charcoal. 

Get the charcoal burning and add green or soaked hardwood later.  You can also buy charcoal with bits of mesquite in it and use it alone.