A load in a circuit is a circuit element that is connected to the output of your device and consuming electrical energy in the circuit, and which can be a simple resistor, a capacitor, a bulb, or even a complicated next stage.
That's to say, if your circuit involves a string of stages connected to each other, then the next stage acts as a load to the previous stage.
In a nutshell, anything that is connected to the output of your circuit is considered as load.
