Cool!

When I've taught things like Standard Deviation in the past I've described it as a measure of consistency, or of how spread out the middle chunk of data is. We teach lots of measures of consistency as we go through school level maths, gradually increasing in their sophistication. For instance we do range, then inter-quartile range and then standard deviation all in an attempt to discern the same thing.

An example: If we are company selling boxes of matches we might put on our boxes that each box has an average (meaning the mean) of 80 matches in it. If we had a competitor that also made boxes with 80 matches in then it might seem that there was little to choose between the two companies.

However if our company's boxes almost always had 79, 80 or 81 matches in and our competitor's had anything from 70-90 matches in, then we would have a much more consistent product, and a much smaller Standard Deviation in the number of matches per box.

Standard Deviation also lets us do other stuff, but at it's core it boils down to this.