Birria vs Barbacoa

I am almost embarrassed to pose these questions, however my family didn't cook either dish so I have no background.

1) Who in Chicago has great birria de res?
2) What is the difference between birria and barbacoa?
3) What does "birria" mean, does it describe a recipe or a cooking process?

I grew up with the assumption that Birria and barbacoa was cooked using only goat meat. It wasn't until I visited Cabo San Lucas a few years back that I discovered a street cafe serving birria de res tacos. Out of this world!! I had never tasted anything so juicy and tender. I started paying attention to menus of other dining establishments and discovered the menu would just say "birria" and not be specific if it was birria de res or birria de chivo.
Can someone straighten this out for me?

OdeM:

Here is a thread that is relevant:
http://lthforum.com/bb/viewtopic.php?p=31325#31325

The following post that I wrote specifically addresses the question of the relationship of the terms 'birria' and 'barbacoa':
http://lthforum.com/bb/viewtopic.php?p=31497#31497

Antonius