A line is a straight, one-dimensional figure that extends infinitely in both directions. It has no thickness and is defined by two points, which are often labeled as A and B. In geometry, lines are fundamental elements used to create shapes and angles. In mathematics, lines can be represented using equations, such as the slope-intercept form, which is written as y = mx + b. Here, m represents the slope, and b is the y-intercept. Lines are also used in various fields, including art, design, and engineering, to create structure and guide the viewer's eye.