If you want to group the results by a particular field value rather than listing all results individually, then you use the GROUP BY keyword.
Here is how the query might look:
SELECT columns FROM Table WHERE clause GROUP BY column ORDER BY column
Common mistakes are to apply the GROUP BY either before the WHERE clause or after the ORDER BY – make sure you get it right.
Also remember that you are returning aggregate data rather than every result as an individual row, therefore it can take a little bit of careful thinking as to when you should use GROUP BY and a realisation of what will be returned when you do.