MOSFETs are also transistors hence their characteristics are very much similar to BJT. Here we are using power MOSFET hence it is capable of handling more power. Motors generally consume more power to operate hence we are using POWER MOSFET here. The use of LDR(Light Dependent Reistor) makes the device more interesting. LDR has the property of changing its resistance as the light falls on it. In the given circuit, we can see that R1 and R2 form a voltage divider network. The voltage at the Gate teminal of the MOSFET increases as the light falls on the LDR. As the Gate voltage of the MOSFET increases, it gets turned on and its Drain and Source gets connected. Clearly, now the current from V3 can flow through Motor M1 and hence the motor operates.