A bar graph is a way to visually represent a set of data. Bar graphs are particularly useful for data that is easy to categorize. The category is traditionally placed on the x-axis, and the values are put on the y-axis.
Bar graphs are very similar to histographs, which are another way to visually represent data. In histographs, however, the data is continuous. Bar graphs traditionally have spaces between the individual bars to keep the graph from looking too similar to a histograph. Bar graphs are also sometimes referred to as bar charts. Other types of graphs include line graphs and pie charts.