A photograph of the financial position of a business at a single point in time. A list of all the assets and liabilities at a single point in time, used by investors, staff, creditors to assess the financial strength of a business.
As a child, you no doubt had a school photograph. At that point in time, you had a pimple, a black eye, or a ridiculous hairstyle. That image was framed forever. Balance Sheets do the same for the assets and liabilities of a company at a single point in time.