Reason - The equator gets the most direct sunlight and energy, so the farther I travel north or south from the equator, there will be less direct sunlight and energy.
They also show the number of dependents (children and, sometimes, elderly people) and general structure of the population at any given moment.
it compares and contrast the age of th female and male where it typically forms the shape of a pyramid when the population is growing which can give you a general idea on both genders
it can help see who (female or male) are the most type in that area
