Net income (or net earnings, net loss, etc.) available to common shareholders represents the income available to holders of common stock. Net income available to common shareholders is important because it forms the numerator of the Earnings Per Share (EPS) calculation:
Net income available to common shareholders are the profits remaining after the company pays all of its suppliers, employees, service providers, creditors, and preferred shareholders. In other words, this is revenue less all expenses and preferred dividends. The number measures common shareholders' claim on the company's cash flows.