Controlling is a managerial function that ensures activities are performed according to plans, resources are used efficiently and effectively, and predetermined goals are achieved. It involves setting standards, measuring performance, comparing to standards, analyzing deviations, and taking corrective actions. Controlling is important for accomplishing goals, improving efficiency, motivation, order and coordination. However, it is difficult to set quantitative standards for some areas and controlling has no impact on external factors or may face employee resistance. Planning looks ahead and prescribes actions, while controlling looks back to check if decisions were implemented and improve future performance.