Heated water and cold water's circulation

In a home with water heater, they differ the water tap into two. One for hot tap and another for a cold one. Each tap has its own circulation. Even though, both has the same source, water tap/reservoir.
For a hot tap, the pipe goes out of the reservoir towards a heater, spinning inside th pipe of the heater and it goes to the highest hot tap in the house. Then, from the highest place, it is distributed down, to a basin, closet, and a bathtub in the second floor. After that, on the next floor, it is distributed only to a sink. Last, leftovers from first and second floor goes to the sewage.
Not quite different from the hot one, the cold one goes to the reservoir too. After that, from the reservoir, the pipe goes directly to the highest cold tap in the house--basin, closet, and a bathtub. Then, the remaining pipe heads to the first floor, to a sink. And finally it goes out to the sewage.