A financial statement showing what a business owns and owes at a point in time: assets = liabilities + equity.
A balance sheet is a snapshot of a company's financial position on a specific date. It lists assets (what the business owns), liabilities (what it owes) and owners' equity.
It always balances on the accounting equation: Assets = Liabilities + Equity. Together with the profit & loss statement and cash flow statement, it shows the financial health of a business.
A balance sheet shows financial position at a point in time (assets, liabilities, equity); a profit & loss statement shows performance over a period (income minus expenses).