Variables

Variables are case sensitive

Variable Naming Convention
cannot start with a number
can contain the underscore character (no other characters)
use "snake case"

__54__ 
one_two 

Variables that are defined as parameters or within a function live until the function ends.
These are local variables.

num1 = 2 
num2 = 6 
sum = num1 + num2 
print(sum) 

A variable should start with letters or underscores (no numbers or special characters)

1var_ = 1   ' syntax error