When a variable is declared, it is accessible in areas of the program that are after where was it declared. For example, if you declare a variable outside of a function, the variable then becomes accessible to code that is run in the function.

Examples

number = 9

def myfunction():
    print(number)

print(number) # 9
myfunction() # 9

The variable number above is what is called a global variable. If we want the number variable to be accessible only inside the function, that is called a local variable.

def myfunction():
    number = 9
    print(number) # 9

myfunction() # 9

print(number) # NameError: name 'number' is not defined.