The 25 kV line down my back lane (Calgary AB) is 3 conductors only.
Drops are made to transformers along the way. The transformers are connected between 2 phases (resulting in single phase delivery) on the 25 kV line, and deliver 110V - 0 - 110V via 3 conductors. (The 0V lead is the N (neutral typically white) conductor.) Overhead drops to houses are via triplex cable. Connection across the two 110V conductors provides 220V which is typically used for heavier loads like electric stoves, clothes dryers, air conditioners and shop tools like table saws and air compressors.
As the 25 kV line continues down the lane, transformers are connected to the next pair of phases, and onto the next pair, providing a balanced load on the 3 phase system. It is more economical to use 3 phase transmission as currents flow counter to each other as you look at the actual current flows, reducing the cable diameters versus what would be needed in a single phase system to transmit the same amount of power.
In commercial and industrial applications, utility power (110V lighting, receptacles, small motors, etc.) is often distributed as 208V three phase wye connected. 120V power is available by connecting to one phase and the center tap of the wye connection.
120V and 110V terms are used interchangeably, as is 220V and 240V in many discussions and specifications as they are within design tolerances. During my electrical education many years ago, what we now call 110V or 120V was simply called nominal 117VAC.