Clarizen API Usage

In some post I've seen some kind of queries like this:

SELECT ExternalId,EntityType,ResourceLink.Resource.Name,Date,DurationInDaysInt,WorkAtDay
        FROM WorkByDay
        WHERE ResourceLink IN (
            SELECT id FROM ResourceLink 
            WHERE Resource IN (
                SELECT id FROM User 
                WHERE Name = 'NAME'
            )
        )

I suppose is CZQL. Is there any endpoint to call to retrieve this information?

Where can I find documentation about Tables, Fields and relationships?

Thanks in advance!