A balance sheet is usually used for businesses and is basically a financial "snapshot" of the business at any specific date in time. It includes the business's assets and liabilities which are added together to calculate the business's net worth.
For individuals, the balance sheet is often referred to as net worth which also lists a person's assets and liabilities. The entire concept isn't too difficult although many people don't take the time to calculate their assets and liabilities. Having a clear view of your balance sheet can go a long way to helping you budget and it is highly recommended that everyone take the time to gather this information and do the calculations to see where they stand. This allows you to track your finances and see how you are doing toward your stated goals.