Laravel $auth calling function as $auth->functionname rather than $auth->function()

I came across some code in Laravel where a function was defined in a user model which extends the Authenticable class. The function is called in a view via $auth, like so:
$auth->function_name
Why is it called this way rather than like so:
$auth->function_name()

from Newest questions tagged laravel-5 - Stack Overflow https://ift.tt/2xb1Sg3
via IFTTT