Originally posted by: Mut@t@
genjutsu messes with the five senses; sight, hearing, smell, taste, and touch. it can't do any actual physical damage. from what we've seen tsukuyomi is aimed for the the opponents' hearing, sight, and touch. i don't know about smell and touch since that's not clearly shown. it didn't do any physical damage to the actual body but it made kakashi's mind think that the body was stabbed for however long it was.
Itachi stated "just because this is an illusion, don't think the pain is fake" or something along those lines. It manipulates the sense of Pain, so therefore tricking your mind and inflicting physical pain. Tsukuyomi, is a mental world, and is manipulated as the user wishes.

Genjutsu is Normaly not real (Tsukuyomi is an exception), it as Mut@t@ said, it only tricks the mind into feeling emotions, and ect. So genjutsu can be concidered more than a illusion, it can be very real, depending on how your mind interprets it.

Zabuza's Mist? It just created extra extra mist. thats about it, or at least it created a false mist. or which ever.

I might be totatly wrong or right, its about 85 degrees here and i cant think!