Kohana ORM “primary value”

[Nexta]

I've been reading through the documentation for Kohana ORM and in their example model class it has a block of code like:\[code\]protected $_table_name = 'strange_tablename'; // default: accountsprotected $_primary_key = 'strange_pkey'; // default: idprotected $_primary_val = 'strange_name'; // default: name (column used as primary value)\[/code\]Obviously I know what table name and primary key are but I've never seen the term "primary value" used before, what exactly is it used for?