What circuits use Current Limiting? as an input or supplying

To set the Current limit on a power supply, you directly short out the positive terminal to the ground on the power supply. that is what my manuals say to do, but is this ok to do? you set the current limiter by shorting out directly

Why doesn't this damage the power supply? what is protecting it from getting damaged?

What circuit use current limiting? as an input or injecting it

Current limiting circuit example:
By Driving current to an op amp or a current comparator to switch the output state , you have to set the current limit

You do not damage the PSU because the current is electronically limited to a safe value. i.e. a 1A PSU which can deliver 1A to a load can deliver 1A to a short circuit (Rl =0 ohms!).
You can only limit the OUTPUT current of a device, the input current is set by the input voltage and the input impedance. Not many other circuits use current limiting as such, normally just a series resistor will do. High power amplifiers will overheat if called on to deliver excess current , so a thermal trip would be used, some times the output current of high power HF transmitters will monitor the output current and will TRIP the transmitter if the current is too high. For a few specialized uses such as dielectric heating, where the actual transmitter load is indeterminate, the monitoring of the output current will reduce the RF output to keep the output current too a safe value.
Frank