I think you are talking about a power supply.
Lets say we have a power supply set to give us 12 volts with a 1 amp current limit.
CONSTANT current:
Place a 24 ohm resistor on the supply. V=12 and 0.5 amps
Load = 6 ohm V=6 and 1 amp.
Load = 3 ohm V=3 and 1 amp.
HICCUP:
Place a 24 ohm resistor on the supply. V=12 and 0.5 amps
Load = 6 ohms. The supply will turn on and see > 1amp and shut down for a short amount of time. Then it will turn on again, then shut down.
FOLDBACK:
Load = 24 ohms V=12 I=0.5
Load = 12 ohms V=12 I=1
Load = 10 ohms V=1 I=0.1
Load = 5 ohms V=0.5 I=0.1
In a over current condition (>1 amp) the current limit is set lower (0.1 amp) until the supply is reset or the load is removed. In this example the fold back is set to 10:1.