What is the difference between power electronic and digital electronics?

This question can be answered in number of ways. The simplest way to say all the electronics devices which deals with power are covered in Power Electronics. There are devices which you do use in general purpose electronics like: Diode, BJT, MFETs etc. You will find these devices in electronics & power electronics both. The devices used in Power electronics may differ in term of construction & behavior from those used in electronics. There are type of devices which you will find only IN PE, ex: IGBT anther answer ordinary devices are low current and low voltage devices. power devices are high current and/or high vlotage devices. ordinary devices generally can be for very high frequency. power devices , again generally, for low to medium frequency. the frequency classification is just for understanding though exceptions are there,

while digital electronics are the devices which work on some logic and the examples are as fallows

MUX,DE-MUX,DECODERS,ENCODERS,ROM,RAM,EEPROM,etc