No matter how great your idea is, most people expect that you have it written down. When I was new to inventing, I had no idea what that meant. I searched around but didn't find any universal format for documenting my ideas.
So, although a detailed business plan may not be required for an online business, I am going to include it here so you can at least look at and consider each section and determine yourself if it applies to your business.
A business plan is a formal statement of business goals, reasons they are attainable, and plans for reaching them. It may also contain background information about the organization or team attempting to reach those goals.
Describe your most important company strengths and core competencies. What factors will make the company succeed? What do you think your major competitive strengths will be? What background, experience, skills, and strengths do you personally bring to this new venture?