Operating income is a key financial metric that shows how much profit a company makes from its core business operations. It is calculated by subtracting operating expenses, such as wages and rent, from gross income, which is the revenue generated from sales. This figure helps investors understand how efficiently a company is running its day-to-day activities without considering non-operating income or expenses, like interest or taxes. This measure is important because it reflects the company's ability to generate profit from its primary activities. For example, if a company like Apple has a high operating income, it indicates that its products, such as iPhones and MacBooks, are performing well in the market.