What is the melting point of ice?In the textbook it is given 0 degree centigrade. But water freezes at 0 degree celsius.Please resolve my confusion.

At melting point is the temperature at which it changes from solid to liquid and freezing point is just the reverse. 

The melting point of ice at 1 atmosphere of pressure is very close  to 0 °C (32 °F, 273.15 K), this is also known as the ice point. In the presence of nucleating substances the freezing point of water is the same as the melting point, but in the absence of nucleators water can super to ?42 °C (?43.6 °F, 231 K) before freezing.