Ahkam (pronounced with a slightly elongated a sound) are laws or rulings. There are six types in Islam:
1. Compulsory (Wajib)
2. Recommended (Mustahab)
3. Forbidden (Haram)
4. Disliked (Makruh)
5. Legal and allowed (Halal)
6. No law defined/required (Mubah)
Most clerics and teachers will only state the first 5 of the laws. The sixth one is essential because it asserts the fact that some things are ambiguous and do not have a legal ruling concerning them.