Population pyramid is used to visualize demographic data. Data is divided into age groups and gender and then one gender is shown on the left side of chart and the right side plots the other gender while age groups are plotted along y-axis in sorted order.

The chart is popularly known as population pyramid because chart looks in the shape of a pyramid because of nature of demographic (though data-sets other than population also can be visualized using pyramids)

Most amazing thing about population pyramid charts is the study of changes over time when the chart is animated.

Population pyramids are very effective to study demographic patterns and comparisons in the data. Sometimes pyramids are animated along the time to see dynamics of the demographic composition over the period of time.

Two or more pyramids can be compared side by side either for same country in multiple years or for multiple countries in the same year.