What does the Numbers Lock key on the computer keyboard do?

It's always there, it's always on.What does the Numbers Lock key on the computer keyboard do?
It makes it so you can use the numbered keypad on the right side of your keyboard.What does the Numbers Lock key on the computer keyboard do?
Hi. Most important on a laptop which uses keys for dual purpose. When ';On'; it uses some of the alpha keys for numerals.
With it being on you can use the number key pad on the lower right of the keyboard - off - you can't.