The IRF830 is a fast switching high voltage N-Channel MOSFET with a low on-state resistance. The Mosfet has a maximum drain to source voltage of 500V. The mosfet will have a drain to source internal resistance of 1.5Ω when triggered with 10V gate voltage.
The IRFZ44N is a N-channel MOSFET with a high drain current of 49A and low Rds value of 17.5 mΩ. It also has a low threshold voltage of 4V at which the MOSFET will start conducting. Hence it is commonly used with microcontrollers to drive with 5V.
The IRF520 is a Power Mosfet with 9.2A collector current and 100V breakdown voltage. The mosfet has a low gate threshold voltage of 4V and hence commonly used with microcontrollers like Arduino for switching high current loads.