Input:
The sensor needs 5V as a supply voltage and it will draw an arbitrary amount of current from the 5V supply as it needs it.
Output:
The sensor provides a 4mA to 20mA output which is proportional to change at the input. You just terminate this output into a load / resistor of your choice and then you've got a voltage over the resistor. They give out 4-20mA because in factories the wires to the respective sensors are sometimes extremely long and transmitting the signal as a current source makes it way more immune to noise.