The select clause picks which objects and properties to return in the query result set. Consider:

select mate
from Cat as cat
    inner join cat.mate as mate

The query will select mates of other Cats. Actually, you may express this query more compactly as:

select cat.mate from Cat cat

Queries may return properties of any value type including properties of component type:

select cat.name from DomesticCat cat
where cat.name like 'fri%'

select cust.name.firstName from Customer as cust

Queries may return multiple objects and/or properties as an array of type Object[],

select mother, offspr, mate.name
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr

or as a List,

select new list(mother, offspr, mate.name)
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr

or as an actual typesafe Java object,

select new Family(mother, mate, offspr)
from DomesticCat as mother
    join mother.mate as mate
    left join mother.kittens as offspr

assuming that the class Family has an appropriate constructor.

You may assign aliases to selected expressions using as:

select max(bodyWeight) as max, min(bodyWeight) as min, count(*) as n
from Cat cat

This is most useful when used together with select new map:

select new map( max(bodyWeight) as max, min(bodyWeight) as min, count(*) as n )
from Cat cat

This query returns a Map from aliases to selected values.