A controller’s position is just under the CFO of a company. The controller is involved in daily accounting, such as preparing reports, budgeting, hiring/firing people in the accounting department, and ensuring compliance. The CFO is part of the executive team, overseas financial strategy, and is often speaking on earnings calls (if the company is public).
In a smaller company, the controller and CFO may be the same position. The controller ultimately handles putting together the financial information that the CFO and other top management use for company strategy.