Lean startup business plans are less common but still use a standard structure. They focus on summarizing only the most important points of the key elements of your plan. They can take as little as one hour to make and are typically only one page.
The business overview or mission should describe how you intend to achieve your vision. For example: how you intend to achieve your vision.
Keep in mind that a business plan is a living document and you can always start with a one-page plan and enlarge it with additional detail as required. You may be able to articulate the business overview, vision, objectives, and concise action items in a single page, but you might want more detail in the financial and marketing sections.