It presents the results of operating the company over a period of time. It details revenues, expenses, and net income. Net income is equal to revenue minus expenses. Revenues are basically sales. They are increases in shareholders' investment due to operating the company.
Expenses are basically the consumption of the company's assets to support operations.
They are decreases in shareholders' investment due to operating the company. Generating profits is generally a primary goal of business. The income statement is basically the company's report card in regards to this goal. The income statement will list the various sources of revenue and the nature and amounts of expenses incurred to earn the revenues. The income statement links the company's beginning balance sheet with the company's ending balance sheet.