What does "chain binding" mean? I'm reading on chain tensioning, the generic idea is that if the chain is too loose it will fall off, if it's too tight it will "bind".

I'm having an hard time understanding what "bind" means in this context. The best I could think of is that the teeth from the cog will be tight to the chain causing both teeth and chain to wear out more easily, but I couldn't find any proof.

These are the sources I was reading:


one is a question on Bicycles: 


  The simple answer is, as Sheldon brown says, as tight as possible without binding.

Second is on Brown's blog: 


  If the chain is too tight, the drive train will bind, perhaps only at one angle of the pedals (chainwheels are not usually perfectly concentric). It should be tight as it can be without binding.
"Chain binding" occurs when the chain is really tight around the sprockets.  No set of sprockets is perfectly round and centered (especially if worn a bit), and if the chain is tight at one spot in the rotation it likely will become too tight with another half-turn or so.  The pressure of the chain on the sprockets makes the crank more difficult to turn, or, if the sprockets are really off-centered (though likely not visibly so) the crank may lock up entirely simply because the chain isn't long enough to reach all the way around.

Even if the sprockets are perfectly uniform and centered, the friction of the chain links against the teeth will contribute to a sort of "drag", if the chain is too tight.

Note that this is different from having a "frozen link", which is a defect in the joining of an individual pair of links in the chain.