A graph is a visual display of some data. In most cases, the data exists in the form of a table. In many cases, the table itself is displayed. However, the same data, displayed as a graph, often creates more impact.
A graph also makes it easier to understand, or interpret, the data that is being presented. When you interpret a graph, you can compare values and spot trends in the data. There are many different types of graphs.
A bar graph is useful for comparing values over time. A bar graph consists of a series of rectangles or bars.
Double bar graph:
A bar graph is also useful for comparing values between groups of items. Such a graph is called a double bar graph.
A bar graph in which there is no gap between the bars is called a histogram. A histogram is useful for showing the distribution of data over intervals.
A pie graph or a pie chart is useful for showing the proportion of each data value to the whole.
A line graph displays data that changes continuously over periods of time. A line graph usually shows a visual comparison between two quantities using a series of line segments. The line segments are joined end-to-end. The line graph, thus, allows us to observe trends easily. This is a major advantage of the line graph.