Line graphs are a powerful way of visually displaying data over a set period of time. They are composed of two axes: the x-axis (horizontal) and y-axis (vertical). The x-axis typically represents time or the amount of data points being displayed in the graph, while the y-axis normally shows the value for each of the corresponding data points.

Line graphs are used in a multitude of different fields to display varying data sets. In finance, line graphs are commonly used to demonstrate the changes in security prices over a certain period of time. By plotting these changes on a line graph, investors and financial analysts can better understand the fluctuations over time of the security's worth.

In addition to charts which display securities prices, other common uses of line graphs include: tracking vehicle sales over a certain period of time, exploring average house prices in a geographic region and mapping the growth of a business’s profits over the years.

Overall, line graphs are an effective way to quickly compare different data sets and trends. They can typically display vast amounts of data, helping to make large amounts of information easier to interpret and visually appealing. Line graphs are generally used to observe changes in the relative values of a specific group of data or the cross-reference of various data points over time. In short, line graphs help to comprehend large amounts of data by connecting the data points on a graph and transforming them into insights.