What does raw_input() function do in python?

The function raw_input() presents a prompt to the user (the optional arg of raw_input([arg])), gets input from the user and returns the data input by the user in a string. For example,

name = raw_input("What is your name? ")
print "Hello, %s." % name

This differs from input() in that the latter tries to interpret the input given by the user; it is usually best to avoid input() and to stick with raw_input() and custom parsing/conversion code.