Since Asynchronized in asp.net is nearly the same as sychronized steps, why we need this?

I know that asychronized can be also done in asp.net. But it seems to be still delayed in technology ……
If so, why should we need that?That looks the same as executed step by step……
http://msdn.microsoft.com/en-us/magazine/cc163725.aspx
Thx
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