While there may be more formal or standard definitions it is generally the end result, so to speak. In a simple circuit where the intent is to supply power to a lightbulb it is the lightbulb that is the load. If you were to design a motor speed controller the motor itself would be the load.
Be careful though because load is a very general term and it does depend on perspective. The speaker connected to your radio can be considered the load - from the point of view of the radio. If you were talking about the AC outlets in your home you might think of the radio that is plugged into the outlet as the load.
It's a reasonable question to ask.