A line graph is a type of chart that displays information as a series of data points connected by straight lines. It is commonly used to show trends over time, making it easy to visualize how values change. The horizontal axis typically represents time or categories, while the vertical axis represents the quantity or value being measured. Line graphs are particularly useful in fields like economics, science, and business for tracking changes and making comparisons. They can illustrate various data sets, such as temperature changes, sales growth, or population trends, helping viewers quickly understand patterns and relationships in the data.