please tell me the function of 16X2 pin functions
A simple Google search will turn up what your looking for. For example:
"A simple Google search will turn up what your looking for" only if you use an appropriate search term.
This information is found in the datasheet for the LCD controller chip on your 16x2 module. Virtually every controller currently used is based on the Hitachi HD44780U so in this case a search for that datasheet will work. My search gave http://www.sparkfun.com/datasheets/LCD/HD44780.pdf as the first hit and this is what you want.
The datasheet found at the previous link only gives the pin names, the HD44780U datasheet actually explains the function of each pin.