Variables are names
Like slope formula above, you can put y1-y2 or y2-y1. Variables are just names in programming (and math).
Let's start with an example.
number1 = 2
I just created a variable called number1
Python is dynamics
In Python, variables and data are in open relationship. No commitment!
The same variable can be used over and over by different type of data (integers, string, images, etc).
Variables are shorthand notation to develop programs. Imagine you have to write your math formula 100000 times. WOW
y = x**4 + x**3 + 2*(x-2)**3 + 10000
z = 2*y + 3*x**2
w = z + y + z + x
print 'your result of w is:', w
the variables x, y, z, w are reusable in this code :)