what is a "moment frame"?

Looking through the simpson strong tie web site I came across this page http://www.strongtie.com/products/strongframe /
They call this structure a "moment frame". So what exactly is a "moment"? Is it something similar to a "bent in" or "bay" as used in a post and beam structure?
Anyone know what they cost? Would they be more than a wood 6x8 post and beam frame?
One video showed them putting together on frame in under an hour. I'd be interested in building a house this way.
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http://tinyurl.com/3kqyu9w kinda
yes http://tinyurl.com/44wguel
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