Wajib - obligatory, necessary, incumbent. An act which must be performed. You will be rewarded for performing it and punished for neglecting it, e.g., the daily prayers, the Hajj (pilgrimage) , Jihad (struggle for the sake of Allah) , the fasting of Ramadhan.

Haram - forbidden, prohibited. It is necessary to abstain from the acts which are haram. If someone performs a haram act, he will be punished, e.g. eating pork, drinking wine, lying, betraying.

Mustahab - recommendable, desirable. An act whose neglect is not punished, but whose performance is rewarded, e.g. the call for prayers (adhan) , saluting others, making ghusl (bathing) for Friday.

Makruh - reprehensible, disliked. An act whose performance is not punished, but whose avoidance is rewarded, e.g. sleeping till sunrise, urinating in stagnant water, eating in the state of janabat.

Halal - permitted, allowed, lawful, legal. An act or the thing which is permitted and lawful. An optional act on which Allah has given us the right of doing or leaving it, e.g., drinking water, eating food, choosing one's work or house.