This document describes linear equations and their graphical representations. It explains that equations of the form y=mx represent proportional relationships with slope m passing through the origin, while equations of the form y=mx+b with b not equal to 0 represent non-proportional relationships with slope m passing through the point (0,b). It also notes that vertical lines have undefined slope since the x-values do not change as y changes. The document provides examples of linear graphs and asks the reader to determine if they represent proportional or non-proportional relationships and write the corresponding equations.