Plans are prepared for the future and are based on forecasts about future conditions. Therefore, planning involves looking ahead and is called a forward-looking function.
On the contrary, controlling is like a postmortem of past activities to find out deviations from the standards. In that sense, controlling is a backward looking function.
However, planning is guided by past experiences and the corrective action initiated by the control function aims to improve future performance. Thus, planning and controlling are both backward-looking as well as a forward-looking function.