Executive Summary: the marketing plan like all the documents that are submitted to established executive bodies must begin with a brief summary of the whole plan, with basic numerical data and info. Mission and Vision: the marketing plan includes the company's "reason of existence", values and its future intentions and strategic approach.
Strategy _ similar to business strategy, marketing plan will capture strategies required to support your business strategy. For example if your business goal is to achieve 20% increase in sales, your marketing strategy would be to 1) introduce new product, 2) increase price for premium offerings, 3) recruit more distributors and offer commission scheme and so on. Strategy is king. When you can see your business in totality, I can assure you that you will find it easier to manoeuvre. Marketing plan is the place to address all these issues.