A linear equation is a mathematical statement that shows a relationship between two variables, typically represented as x and y. It can be written in the form y = mx + b, where m is the slope and b is the y-intercept. The graph of a linear equation is a straight line, which means that the relationship between the variables is constant. Linear equations are used in various fields, including science, economics, and engineering, to model real-world situations. They help in predicting outcomes and understanding trends by establishing a clear connection between different quantities.