Start by writing a description of your business, including what stage of development it is currently in (conception, start_up, first year, mature, exit) and your plans for growth. Discuss the nature of your business, the main products and services you offer, the market for your products and services, and how and by whom the business is operated.
Explain the fundamentals of the proposed business: What will your product be? Who will your customers be? Who are the owners? What do you think the future holds for your business and your industry?
If an online business, you need to go into detail how you will attract customers to your website. General statements like "I will use Face Book ads and email marketing" will contribute almost nothing to helping your cause unless you have detailed statistical analysis of tests you have conducted or of another similar business you have been associated with. If you do not have any data upon which you reference your estimates, it could show lack of proper thought to the remainder of your business plan.
The next section, themarketing plan, gets into the details of what your business offers and what market it serves. Marketing is the communication of how your products and services "ease customer pain." Show the problem and how your business solves it. Marketing is a necessity for every business because once your doors are open, you must invite customers to come in. Everything you do in your business that affects customers is marketing because it sends a message about your company.