Modules are code files meant to be used by other programs. In order to use a module, we use the import statement. A module can import other modules. 

Let's discuss the simple Python program:

def sum1(a,b):
 c = a+b
 return c

def mul1(a,b):
 c = a*b
 return c

The preceding code is a very easy and basic example. Let's save the program as module1.py. You can consider that the preceding program is the Python module. We will use module1.py. Consider, while making another program, you need multiplication or addition of two numbers. You need not make any function. You can take the advantage of module1.py.