As an example, concretely I might have a list of people's heights and ages. I can attempt to fit a line to match heights as a function of age. Abstractly, I mig

As an example, concretely I might have a list of people's heights and ages. I can attempt to fit a line to match heights as a function of age. Abstractly, I might have a list of numbers x and y. I can attempt to fit a line to them too. More abstract, but no more complicated.