What is Bulgur ?

Bulgar is a type of grain.
For information here is a link to Wisegeeks and "What is Bulgar?". Cheers!

Mixed vegetable bulgur makes for a fantastic side dish alongside almost any meal. It is also just happens to be a great way to incorporate plenty of vegetables into your meal. Plus, there is the added bonus of honing your knife skills at the same time.

I also wanted to mention that one should not get hung up on exact amounts when it comes to adding the vegetables, as this recipe is quite flexible. In fact, I often use about twice the amount of vegetables when I make it.

Is there any reason to stir vegetables when you're sweating them in a nonstick pan, or is it better to just leave them alone?

Thanks,
Michelle

When sweating vegetables there are no hard rules about when to stir and when to not stir; however, with that said, initially they should be stirred to ensure they are evenly coated in the fat and after that they should be stirred occasionally to ensure they evenly cooking (ingredients that are on the bottom will cook quicker as they will be in direct contact with the pan). Hope this helps. Cheers!

Can pearl barley be used instead of bulgur?
What should I keep in mind if I make the substation?

Yes, any grain can be substituted. You will find it helpful to review the lesson on How to Cook Grains in the Cooking School. Here you will find many answers to your question. Cheers!