A population pyramid, also called an "age-gender-pyramid", is a graphical illustration that shows the distribution of various age groups in a population (typically that of a country or region of the world). Males are conventionally shown on the left and females on the right, and they may be measured by raw number or as a percentage of the total population.
The overall shape of the pyramid shows if a country's population is relatively young, in which case the base would be wider than the top, or relatively old, which would show a wide top and a narrow base. The relative length of the horizontal bars shows if there are more females than males, or viceversa, within each age group.