This sort is exposed. If you hide it, users will not be able to change it.
This will appear in the URL after the ?, as value of 'sort_by' parameter, to identify this sort field. Cannot be blank. Only letters, digits and the dot ('.'), hyphen ('-'), underscore ('_'), and tilde ('~') characters are allowed.
Order
This title will be displayed on the views edit page instead of the default one. This might be useful if you have the same item twice.