l have a Nissan Cefiro V6 2000 cc and there is a Switch near the Gear box marks A/T and Power. What does that do?

Most modern vehilcles with automatic trasmissions have a version of this. As these trasmissions r electronically controlled, the switch merely (electronically) changes the shift patterns of the transmission eg in Power mode, the engine revs higher before each change giving a sportier performance (and a substantially higher use of expensive fuel). Some vehicles also have a position marked with a snowflake symbol which is mostly designed for taking off in icy conditions. With this shift pattern, the transmission begins in 2nd or 3rd gear to give a more gradual transmission of power to prevent loss of traction.