It is outline of the business giving details of the finance, assets, staff, products or services and markets. It guides the entrepreneur, it identifies possible problems and it is also used in funding applications. The business plans sets out how to owner of a business intends to realize its objectives.
Remember the proverbial expression 'not seeing the wood for the trees'? You need to see the 'wood' first, then delve in and start examining the individual 'trees', meaning the individual items which you will be breaking down later. So a great point is to make sure that you have that overarching vision - and if you cannot find one, then maybe it is an indication that you are obsessing on a few technical aspects that do not necessarily make up a whole business as you had imagined it.
Be Prepared For Risks : It is a fact of life that any new business or enterprise has a degree of risk attached to it. Therefore it is important for your business plan to analyse and calculate that risk, showing how you will engage with it. There is no business plan out there that is risk-free, but very often where the risk is higher then the rewards will be as well.
I say that because of course you need to be careful with commercially sensitive ideas, as you do not want to pass your plan on to someone in the pub who then starts your idea before you across the road.