The difference is source of power supply for input signal.
Built-in power supply ・・・ Use the power supply which is installed in Driver.
External power supply ・・・ Use the power supply which is provided external device.
Example : Power supply in PLC (Control devise).
Caution : Wiring is different by using whether Built-in power supply or External power supply
Please refer Instruction manual "7. Connection method for I/O terminal" .
Click"here" for download Instruction manual.
References
・You cannot use source connect on Built-in power supply.
・Only External power supply can be used for Output signal.