What does this recursive method do$?$

private int method$($Node node$)$

$\{$

if $($node $==$ null $)$

return $0$;

else if$(($node$.$left $!=$ null && node.right $==$ null$))$

return $(1+$ method$($node$.$left$))$;

else

return $($method$($node$.$left$)+$ method$($node$.$right$))$;

$\}$