Hiding Nodes/Hiding Meshes - Basic Info

I'm trying to understand everything about these sources:

Hiding Nodes in a Model:
http://www.garagegames.com/index.php?sec=mg&mod=resource&page=view&qid=2150

Hiding Meshes:
http://www.garagegames.com/index.php?sec=mg&mod=resource&page=view&qid=5421

Can anyone kinda explain this in a dumbed down fashion to me? I think I understand the first one - I'm guessing if you hide a shoulder node, the arm attached to it disappears, etc. I could be wrong.

But the meshes one confuses me most - are they talking about putting all these different armor meshes on the model, or in the milkshape having several armor models just floating next to the model, and when they're switched to they APPEAR on the model inside torque? I can't imagine trying to manage a model with 20 armor suits all situated in exactly the same spot.

Just pretend you're talking to someone with almost no 3d modelling experience (me) and tell me:

precisely what a mesh is
precisely what the node hide does and how it works
precisely what the mesh hide does and how it works

Anything would be a help. Thanks!

Glez