This document discusses linear regression and its use in modeling real-world problems. It defines linear regression as finding the linear function that best fits a set of data points. The document provides an example of using a graphing calculator to perform linear regression on price and weight data for emeralds. The calculator outputs an equation for the line of best fit as y = 5475x - 1042.9, providing a simple mathematical model to describe the relationship between an emerald's price and weight.