Fine! Lastly, we're going to show you a more advanced trick: CASE WHEN with GROUP BY. What is it about? You can actually group your rows by the values you provide yourself in the CASE construction. Take a look:

SELECT
  CASE
    WHEN fee = 50 THEN 'full_fee'
    WHEN fee = 10 THEN 'reduced_fee'
    ELSE 'no_fee'
  END,
  COUNT(fee)
FROM application
GROUP BY CASE
  WHEN fee = 50 THEN 'full_fee'
  WHEN fee = 10 THEN 'reduced_fee'
  ELSE 'no_fee'
END;

The result of this query will show groups 'full_fee', 'reduced_fee' and 'no_fee' with the number of rows containing these values. Of course, you could achieve similar results by using COUNT or SUM with CASE WHEN.

Here, we just want you to realize what possibilities CASE WHEN gives you. Note, however, that this time you'll get 'full fee', 'reduced fee' and 'no fee' as separate rows, not as possible values of a single column.