If you are confused between the append and extend methods, the following example will clear your doubts:

>>> Linux  = ["kali", "Ubuntu", "debian"]

>>> Linux2 = ["RHEL", "Centos"]

>>> Linux.extend(Linux2)

>>> Linux

['kali', 'Ubuntu', 'debian', 'RHEL', 'Centos']

>>>

>>>

>>> Linux  = ["kali", "Ubuntu", "debian"]

>>> Linux2 = ["RHEL", "Centos"]

>>> Linux.append(Linux2)

>>> Linux

['kali', 'Ubuntu', 'debian', ['RHEL', 'Centos']]

>>> 

The append method gives a list within the list. The list Linux2 = ["RHEL", "Centos"] has been taken as one list. Let's proceed to the next method.