What is meant by Pareto Chart?

One of the seven tools of quality control, it is a bar graph that displays variances by the number of their occurrences. Variances are shown in their descending order to identify the largest opportunities for improvement, and to separate 'critical few' from the 'trivial many.' Also called Pareto diagram.

A pareto diagram is used to graphically summarize and display the relative importance of the differences between groups of data.

A Pareto diagram can be used to quickly identify what business issues need attention. By using hard data instead of intuition, there can be no question about what problems are influencing the outcome most. In the example below, XYZ Clothing Store was seeing a steady decline in business.

Agreed with Mr. Helal answer,

80-20 rule

is a vertical bar graph in which values are plotted in decreasing order of relative frequency from left to right. Pareto charts are extremely useful for analyzing what problems need attention first because the taller bars on the chart, which represent frequency, clearly illustrate which variables have the greatest cumulative effect on a given system. 

The Pareto chart provides a graphic depiction of the Pareto principle, a theory maintaining that 80% of the output in a given situation or system is produced by 20% of the input.

A parato chart is used to graphically summarize and display the relative importance of the differences between groups of data.

agreed with Mohammed Helal answer

I apologize for the answer I leave the answer to the experts, specialists in this field that's not my area I wish you only invite specialists only

thanks for invition ,,,,,,,,,, i agree with experts answers

Its a simple bar chart that ranks related measures in decreasing order of occurrence and its based on Pareto principle.One among the 7 basic tools of quality control