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 fasting of Ramadhan.
Ihtiyat wajib‑precuationarily obligatory. Its significance is the same as that of wajib with the difference that in the rules where a mujtahid says it is "precautionarily obligatory", you have the option of leaving his taqlid (following) in that particular problem, and following the rulings of the second‑best mujtahid in that problem.
Mustabab, Sunnat‑recommendable, desirable, better. The acts whose neglect is not punished, but whose performance is rewarded, e.g., the call of prayer (adhan).
Ihtiyat mustabab‑precautionarily recommended. Its significance is the same as that of mustahab. When a mujtahid uses this term, he means that there is no solid proof for that particular act being mustahab, but his standards of precaution demand that it be considered as mustahab.
Ja'iz, Halal, Mubah‑permitted, allowed, lawful, legal. The act or the thing which is permitted and lawful. There is no reward for performing it and no punishment for neglecting it, e.g., drinking tea. Mubdh is mostly used for lawful things, not for permitted actions.
Makruh‑reprehensible, disliked. The acts whose performance is not punished, but whose avoidance is rewarded, e.g., eating in the state of janabat.
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.
Junub‑a man or a woman who has become najis (impure) because of sexual intercourse or, in the former's case, because of discharge of semen.
Qaza‑performing an act of worship which was missed during its proper time.
Musalla‑place or mattress of prayers.
Rak'at‑a bending of torso from an upright position in prayers.