A bar chart is useful when you want to do a quick side-by-side comparison of categorical data (e.g., countries, colors, types ...

A line graph shows how data changes over time. For example, how the volume of traffic changes over a day so you can see the busiest times. A bar chart is best for comparing groups of data.

Note how the total adds up to 100%. Bar charts and line graphs can be combined. Climate graphs are an example of this. The x-axis shows the months of the year and there are two y-axes to show ...