plz see this code

x=raw_input('enter any number :')
def adder(d):

in this function when x is passed to function adder ,,is 'x' and 'd' are copy of each other or d is reference of x..

A print statement should clear it up.
Here first line get run,where user input return an integer.
Then that integer is passed inn as an agument to function adder.

Then d take that value and put result in a new variable d.
Then we print out result.
Because of bad name to variables,this get more confusing than it should be.

x = int(raw_input('enter any number :'))

def adder(d):
    d = d + 1 
    print d


well said ;)

Also d is just there to show the type of variable the method can use. int,char,float ...etc.
But in python variables types are not much worried about since python takes care of that.

Python does "duck typing", look at this example ...

def adder(d):
    d = d + d 
    print d

x = 1
adder(x)  # 2

x = 1.5
adder(x)  # 3.0

x = 'bon'
adder(x)  # bonbon