جَاءَ الْوَلَدُ ضَاحِكًا
The boy came laughing.
- جَاءَ is the action: came.
- الْوَلَدُ is the subject and the one whose condition is described.
- ضَاحِكًا tells his condition while coming. It is mansub as haal.
Remove ضَاحِكًا and the basic event still remains: the boy came. Haal adds the condition in which it happened.