O2 optimize and normalize

[Rudedog]

I haven't seen these two functions explained and was just curious. Can someone explain to me when you would use these and what the end result would be?

OPTIMIZE
I get the idea but don't really notice any difference when I try it.

Redefine & Normalize (right-click in named selection box)
I am familiar with the redefine part, but not the Normalize end of it.

[Kegetys]

Optimize combines vertexes that are "on top" of each other, so for example if you do a two-sided face by copying the face over itself and then reversing it, you will end up with 3 (or 4) extra vertexes because the vertexes are copied too. Running optimize will fix that by assigning the two faces into the same 3 (or 4) vertexes. Its generally a good thing to use, but the combining can also cause problems with animations for example, since it can combine vertexes that are supposed to come apart at some time (like when opening a canopy).

[BraTTy]

I am not completely sure but I recall using optimize on my whole plane and it messed up alot of parts (made my canopy part of the plane)
I would be careful and only use it on non alpha parts of the model (says that it optimizes for use in OFP)
I use it on the main frame of the model after I model it

Redefine and normalize...I know redifine is just redefine its named selection ,I think its main use is for copy of parts,lets say you copy a seat to a back seat that has some named parts.
Copy and paste,rename your selections ,then when you pick redefine and normalize it sets the new named selections and normalizes the faces to change for the diff lighting (same as F5 I believe)

edit: ahh Kegetys posted same time,just I took longer