Learn in the textbookFundamentals of Profit and Loss Calculation
DefinitionOperating profit (営業利益) is the profit earned from the core business: gross profit minus selling, general and administrative expenses (販売費及び一般管理費, or SG&A, 販管費).
ExplanationSG&A covers the costs of selling goods and running the company, such as advertising, sales staff salaries and head office rent. Interest received or paid and similar items arising outside the core business are non-operating income (営業外収益) and non-operating expenses (営業外費用), and they are left out of operating profit. After operating profit come ordinary profit (経常利益), which adds and subtracts the non-operating items, and finally net income for the period (当期純利益), after one-off extraordinary gains (特別利益), extraordinary losses (特別損失) and corporate taxes.
AnalogyFor an online shop, what is left after paying for ads and office rent out of the margin on goods sold is the profit from running the shop, its core business.
Memory hook営業 means the core business. Interest that arises outside it goes under "non-operating" (営業外), so the names themselves tell them apart.