Throttling a processor means to force the processor to stay in a deeper idle/sleep state for a while.
This can be useful if your system is just under light load.
Tasks will be hold up until the cpu is waken up again.
This throttling is independent from the systems emergency throttling that is used if your processor gets too hot.
Please note that you should try throttling the first time if there is no danger that you'll lose data (like an unsaved document, etc).
On some systems the highest throttling state can freeze the system.