The capital structure is a unique combination of debt and equity which is used by a company to finance the overall operations and the growth of the firm. The Debt comes in the form of bond issues or loans, while the equity which may come in the form of common stock, preferred stock, or in the form of retained earnings.In a capital structure, the equity is the company's common and the preferred stock plus its retained earnings. This combination is considered as the invested capital which appears in the shareholders' equity section of the balance sheet. The Invested capital plus the debt comprises the capital structure.