A Pareto chart is a special type of vertical bar chart that helps you focus your efforts on manufacturing problems that have the greatest potential for improvement. A Pareto chart can focus attention on the defect/problem associated with the greatest cost or the greatest number of incidences. These charts are most effective when the ordering of the defects/problems is not changing over time. In the simplest terms, a Pareto chart is a quality tool that helps you identify the most frequent defects, complaints, or any other factor you can count and categorize.
The basic structure for a Pareto is the same as a histogram.
In a Pareto chart, individual values are represented in descending order by bars and the cumulative total is represented by a line. More information: Pareto chart (Wikipedia.org)