Map Range Unclamped

What is the node of Map Range Unclamped used for?I can not understand it.Can anybody help me ?

This node is pretty straight-forward. It essentially finds the alpha of Value from InRangeA to InRangeB, and applies that alpha to OutRangeA and OutRangeB, to give you a return value.

Let’s say you have a number that is from 0 to 1, and you want it to instead be from 100-200. You could multiply it by 100, and add 100, OR, you could use this node. In that case, your in ranges would be 0 and 1, and your out ranges would be 100 and 200. If Value was 0, it would output 100. If Value was 0.5, it would output 150. If Value was 1, it would output 200. The Unclamped portion of the node just means that it will not clamp the return value between Out Range A & B.