Finally we're writing the all important Executive Summary to the Business Plan. And, of course, it has to be concise.
(Most advice also says to write it last, but I think it's a good starting point as an outline of all the points you will cover in more detail - so I recommend that you do a draft Executive Summary first.)
But the final objective is prepare a brief (1 - 3 page) summary of the key points in your Business Plan, which might be a 20-page document or more, plus all the supporting data in appendices.
An excellent guide to the Executive Summary is available at Garage Technology Ventures (Garage.com). They emphasize that aside from being concise and still answering all the important questions the Executive Summary is primarily a selling tool for your Business Plan. It allows potential lenders, investors or strategic partners to quickly decide if they are interested in participating in your plan.
And even more important than the executive summary is that one sentence or paragraph in your cover letter or e-mail (or elevator pitch) that convinces them you may be onto something that could be a viable business.