My multimeter contains resistors which are inserted inline on the mA ranges.
On the 300 mA range, it inserts a 1 ohm resistor. It is in parallel with the meter.
I have never thought in terms of using these internal resistors for any purpose except as connected with the meter. I suppose if I wanted, I could hook the meter up to use the 1 ohm resistor for some external purpose.
There is a certain voltage which will pin the meter. I calculate it as .3 V because I would read 300 mA through 1 ohm (and 300 mA is the range which applies the 1 ohm resistor).