A line chart is a type of graph that displays information as a series of data points connected by straight line segments. 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 values being measured. Line charts are useful in various fields, including business, science, and economics. They help in comparing multiple data sets by using different lines, allowing viewers to quickly identify patterns, peaks, and troughs in the data.