Everything you own minus everything you owe.
Net worth is the total value of your assets — cash, investments, home equity, retirement accounts — minus your total liabilities such as mortgages, student loans, and credit-card balances. It is the single clearest snapshot of financial health, and tracking it over time matters far more than any single month's number.
Someone with $250,000 in assets and $90,000 of debt has a net worth of $160,000.