Saw this simple sprint iteration and releases comparison chart in a Rally training page. I like the line on the difference of focus - release is "what" and iteration is "how." Just keeping that in mind will help guide sprint planning meetings much better. Also, given that the focus of sprint planning is task-estimating, not story-writing, the assumption is that the top of the product backlog (sprint backlog) is well groomed. Taken from Rally's Agile Planning Step-by-Step Guides.
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