how does extend work in python code example

Example 1: python append vs extend

my_list = [23, 11, 42, 24523]

# append will add it as if you're adding a new list to it
my_list.append([34523, 76979])
print(my_list)

# extend will go over each item in the new source list and add each
# element as part of the target list (my_list)
my_list.extend([12, 99])
print(my_list)

""" 
Output:
[23, 11, 42, 24523, [34523, 76979]]
[23, 11, 42, 24523, [34523, 76979], 12, 99]
"""

Example 2: extend in list python

subjects=["Maths","Science","Arts","Commerce"]
subjects_2=["Artificial intelligence","Statistics"]
subjects.extend(subjects_2)
print(subjects)  ## used to add more elements from other list