A function is, at a basic level, a block of code that can executed, not when written, but when called. So let's say I have the following piece of code, which is a simple multiplication function:
def multiply(x,y):
return x * y
So if I called the function with multiply(2,3), it would return the value 6. If I modified the function so it looks like this:
def multiply(x,y):
print(x*y)
return x*y
...then the output is as you would expect, the number 6 printed. However, the difference between these two statements is that print merely shows something on the console, but return "gives something back" to whatever called it, which is often a variable. The variable is then assigned the value of the return statement in the function that it called. Here is an example in the python shell:
>>> def multiply(x,y):
return x*y
>>> multiply(2,3) #no variable assignment
6
>>> answer = multiply(2,3) #answer = whatever the function returns
>>> answer
6
So now the function has returned the result of calling the function to the place where it was called from, which is a variable called 'answer' in this case.
This does much more than simply printing the result, because you can then access it again. Here is an example of the function using return statements:
>>> x = int(input("Enter a number: "))
Enter a number: 5
>>> y = int(input("Enter another number: "))
Enter another number: 6
>>> answer = multiply(x,y)
>>> print("Your answer is {}".format(answer)
Your answer is 30
So it basically stores the result of calling a function in a variable.