SQL & PL/SQL

I have little query about GROUP BY clause.

Sometimes we will give multiple column names in GROUP BY .If it behaves in the same way as ORDER BY (multiple columns) i would love to have an example where I can use GROUP BY multiple columns. Anyways howsoever it behaves it will be really appreciated if anyone can explain a scenario where GROUP BY with multiple columns can be used.

I know about the usage of aggregate functions with GROUP BY but using only one column.

Thanks..!!!