We collect water from a catchment basin, whether a river or underground aquifer. The percentage that comes from underground versus surface water varies from region to region. Unless it is already of very high quality, the water  then undergoes various  treatment processes that remove any contaminants that could be harmful to human health. This is particularly the case for water obtained from surface sources.
The collected water is then stored in reservoirs until it is delivered to the community through a network of mains and pipes called a distribution system.