Goodness of fit

Goodness of fit is like a grade you get when you try to make something fit together. You compare a thing you made to the thing you are trying to make it fit to, and then you see how good of a job you did. For example, if you were trying to make a puzzle and you had all the pieces, but some of them didn't fit together well, that would mean you didn't get a good score on the goodness of fit. If all the pieces fit together perfectly, that would mean you got a perfect score for the goodness of fit.