This is a map of the number of people estimated to be living in households that are connected to a water supply. Water is supplied to households rather than to individuals, so data collected refers to household water supplies.
In Western Europe almost all households have tap water supplied; in Central Africa only 10% do. Having water pipes connected to your house means that you do not need to spend time and energy collecting water for drinking, cooking and washing. Piped water is necessary for the operation of a flush sewage system.