How are the individual homes connected in a 3 phase power distribution system (power grid) so that they have correct voltage?
For most residential power in the USA, there are transformers that are dedicated to single-phase residential power distribution. Each transformer has the primary side connected to the distribution voltage that is thousands of volts. The exact voltage of the primary and the connection details are not important for this question. The secondary of the transformer is 240 volts with a tap in the center of the winding so that higher power residential loads like a clothes dryer or central air conditioner can be connected to 240 volts. Two groups of `120 volt circuits are connected between the center-tap neutral and one or the other of the ends of the winding. In that way, the 240-volt service is split into 120-volt services.

The transformers for residential service are located on the power poles or on concrete pads where they serve a neighborhood or part off a neighborhood. An apartment building may have a transformer inside the building.