A goal, the final purpose is a concrete description or characterization of single situation at a point in time. One can have the goal to achieve a specific purpose.
Also, the goal can be decomposed into subgoals. For example, during winter, it may be cold in a house. The purpose to keep us warm in the house can be achieved in different ways, such as turning on the radiator of a central heating system or turning on an air conditioner in heat mode. The goal can be set to maintain room temperature at 20°C.