Differences are : Peak Repetitive Reverse Voltage of 1N4001 is 50V while that of 1N4007 is 1000V. RMS Reverse Voltage of 1N4001 is 35V while that of 1N4007 is 700V. Typical Junction Capacitance of 1N4001 is 15pF while that of 1N4007 is 8pF
These diodes are built for rectification and other general purpose tasks in electronic circuits. Mostly it is used in the power supply section of electronic appliances to convert AC voltage to DC, blocking of voltages on desired places in the circuit etc
