Single phase and three phase are the parameters in electricity… Single phase has a voltage rating of 220-230v wit 50 Hz freq in India. And three phase is 415v wit 50 Hz freq India.
Well in single phase there is one phase and one neutral i.e. P and N while in three phase there are three phases i.e.R,Y,B and a neutral both are dislaced by 120°each.
This is the main difference between single and three phase. And in three phase there are two ways to connect the three phases one is star and another one is delta. In star each phases of one end are connected at one point which forms neutral. In delta each phase is connected to end of other phases so thus it forms a closed path with no neutral.
Three phase is economical in operation and used in transmission and large machineries,while house holds use single phase.
One of the major difference between the single phase and the three phase is that the single phase consists one conductor and one neutral wire whereas the three phase supply uses three conductors and one neutral wire for completing the circuit.