What is the difference between temporary and permanent mahram relatives, and is it permissible to sit with temporary mahram relatives, laugh, and show one's hair in front of them during the period of prohibition?

It is permissible for a woman to sit, be in seclusion, travel, and uncover non-awrah parts of her body in front of her permanent mahrams (unmarriageable kin). These are individuals with whom marriage is eternally forbidden for her, unlike temporary mahrams, with whom marriage is forbidden due to a temporary impediment that will eventually cease. The awrah of a woman in front of her permanent mahrams varies: the Malikis and Hanbalis hold that her awrah is everything except the face, head, hands, and feet. The Hanafis consider it to be from the navel to the knee. The Shafi'is permit a man to look at anything on his mahram except what is between the navel and the knee, provided there is no fear of fitna (temptation).