The business plan is a document used by the entrepreneur of a project as an analysis tool. It is also a letter of introduction that describes to third parties your business model and it helps you to handle negociations with strategic and financial partners, etc. 
A good business plan follows comprehensive guidelines for both form and content, it must be clear and concise but, at the same time complete; it must content all the essential features of your company. It must be coherent and enthusiastic.