In Python's collections module, most_common() is a method of the Counter class that returns a list of the n most common elements and their counts in the Counter object. The elements are returned as a list of tuples in descending order of their count.

Here's an example of using the most_common() method in Python:

from collections import Counter
 
# Create a list of elements
elements = ['apple', 'banana', 'apple', 'cherry', 'banana', 'apple']
 
# Create a Counter object from the list
element_count = Counter(elements)
 
# Get the two most common elements and their counts
most_common = element_count.most_common(2)
 
# Print the most common elements and their counts
print(most_common)
In this example, we create a Counter object from a list of elements and use the most_common() method to get the two most common elements and their counts. The output will look like this:
[('apple', 3), ('banana', 2)]

You can change the value of n to get a different number of most common elements. If n is not provided, most_common() returns all the elements and their counts in the Counter object.

from collections import Counter
 
# Create a string of characters
s = 'mississippi'
 
# Create a Counter object from the string
char_count = Counter(s)
 
# Get all the most common characters and their counts
most_common = char_count.most_common()
 
# Print the most common characters and their counts
print(most_common)

In this example, we create a Counter object from a string of characters and use the most_common() method without any argument to get all the most common characters and their counts. The output will look like this:

[('i', 4), ('s', 4), ('p', 2), ('m', 1)]

most_common() can be a useful tool when you need to analyze the most frequently occurring elements in a collection, such as words in a text or items in a sales report.