Well, i can’t stop making newbie-questions…
apologies :S
But, whats the func. off the tab-key??
Its seems to “smooth” the hole model, but technically it isnt smooth…
and the other doubt is in which “mode” do you model? with the tabkey on or off??
thanks 
sacslacker is correct. It toggles between Sub-D and polygonal mode. Just to add a little info; It’s not just a visual thing (not implying that that’s what sacslacker was suggesting). When you Tab from one state to the other you are in that state. While modeling sometimes it is faster to move around in the ploy mode. You can however have both Polys and Sub-D’s in the same mesh layer. If you Tab one of those layers the states will simply switch for each group. If you hit the render button while in poly mode it will triangulate all the polys and render them. If you render from the Sub-D state it will tessalate the model and then render it out.
Curt
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