SELECT clause must contain SELECT and FROM keywords in the following order:

SELECT ... FROM ... 

It specifies which fields and from which table should be extracted.
WHERE clause is optional and is used to impose additional restrictions on the data that is extracted.

SELECT ... FROM ... WHERE ... 

Other clauses and keywords may also be used in a query. For example, in the following way:

SELECT what_fields 
FROM which_table 
WHERE some_conditions
GROUP BY some_field
ORDER BY some_field
LIMIT number_of_records_to_return