MS Project Task Types - Fixed Work - Units - Duration

Upon reviewing a vendor's Integrated Master Schedule, created in MS Project, I noticed something very peculiar. Where some tasks could clearly be marked as Fixed Duration, everything was Fixed Units.  I think there are two answers for this.  Either there was a misunderstanding about the work to be performed or the person doing the schedule needs some help understanding task types.  I believe working with MS Project can make your eyes bleed if you're not used to it.  But if you're armed with just a little information about task types, it can be a whole lot easier. I would love to go into a detailed explanation about Fixed Work, Fixed Units, and Fixed Duration.  If I did, however, you'd probably leave my site never to return.   Instead, I found a very helpful video on YouTube.  Why go hunting for this stuff when you can just find it here?