Answer:
   
   Judaism has three mourning periods for immediate relatives. The first
   is Shiv'ah, the seven days starting at the time of interment. Since
   the Hebrew calendar day begins at sundown, the evening of the funeral
   is actually the second day. The basic rules for shiv'ah (lit: 7, the
   first week after burial) are as follows:
    1. One wars the garment torn at the funeral.
    2. One does not wear leather shoes, but other leather clothing is
       allowed. Typically, one wears slippers.
    3. One does not eat meat.
    4. One does not bathe their entire body (except as needed for basic
       sanitation, and as preparation for Shabbat), nor wear cosmetics.
    5. There is no sexual intimacy.
    6. One sits on or near the ground. Typically, one sits on low wooden
       stools.
    7. One does not cut their hair for 30 days (including shaving, for
       men)
       
   Additionally, mirrors are covered, and Religious Services take place
   morning and evening where the mourners can recite the Kaddish, a
   doxology acknowledging the greatness of G-d.The last day one arises in
   the morning, walks around the block, and Shiv'ah is over. Thus, the
   period is actually five days, surrounded by a few hours on each end.
   During Shiv'ah, we remain at home and refrain from just about all
   activities.
   
   Why does Shiv'ah have these rules? If you note, all relate to signs of
   physicality. Shoes are to the body as the body is to the soul; both
   "cover" the lower extremity of the other. Hair care is symbolic of
   fashion and concern with appearance. Meat, furniture and sex are
   physical pleasures. Confronting death is a time at which one can
   reaffirm in themselves the idea that man is more than a clever mammal.
   To spend time thinking about our physical selves would waste that
   opportunity. The whole procedure, having you interrupt your life for a
   definite period of time, is quite cathartic. By having the duration
   fixed, one doesn't feel that they short-changed their love-one's
   memory.
   
   When Shiv'ah is over, we enter a period called Sh'loshim, which means
   thirty. This period actually includes Shiv'ah, so in effect, it is
   only twenty three days long. During this time, we get back into the
   outside world. This would include going to work, pursuing volunteer or
   political activities, or return to school. In other words, we get on
   with the activity of life. However, we do not go to parties or other
   "light hearted" events. The Kaddish prayer is recited at three daily
   services for 11 months.
   
   On the thirtieth day after interment, official mourning is over,
   except for the year long mourning period for a parent, during the
   first eleven months of which, one is obligated to say Kaddish daily.
   All of the above is according to Halachah (rabbinic law).
   
   On the anniversary of the death, every year, those who losed loved
   ones recite the Kaddish prayer. Four additional times during the year,
   memorial prayers are recited at the synagogue. The earliest reason for
   Kaddish was to elevate the soul of our loved ones to a high level in
   the Olum Haba, (heaven or literally, The World to Come) Additionally,
   there are many psychological reasons for remembering parents and
   relatives.
   
   Note that Shiv'ah, and the practices during it, are a Rabbinic
   enactment from the late 2nd Temple period.
   
   Many Reform Jews observe Shiv'ah for only three days. Many do not
   observe Sh'loshim at all. Many do come to synagogue every Friday night
   for a year to say Kaddish.
   
   So who should say Kaddish? The traditional laws governing mourning is
   that a son (child) is obligated to sit shiva and officially perform
   the Jewish mourning rituals. It doesn't apply, in traditional Judaism,
   to grandchildren; in such cases, the obligation would fall on the
   grandchild's father and any uncles. Traditional Judaism, in fact,
   prohibits reciting Kaddish if your parents are alive. Sometimes
   (again, in traditional practice), people hire someone to recite
   kaddish for them if they are unable to attend the synagogue, or are
   unable to participate in a minyon (for example, a daughter).
   Progressive movements, such as Reform, permit anyone to say Kaddish
   for someone they wish to remember.
   
   The first reference to remembering the dead on Yom Kippur is found in
   Orkhot Khayim by Rabbi Aaron HaKohen of France of the 14th century. It
   is also mentioned earlier that there was a practice at the time of the
   Maccabees of "taking a collection amounting to 2000 silver drachmas
   from each man and sending it to Jerusalem... to pray for the dead...
   to make atonement for the dead so that they might be set free from
   their sin." (II Maccabees 12:43-45). Formal Yizkor remembrances were
   instituted in the 19th century by the earlier reformers. The custom
   began to be incorporated by other branches of Judaism shortly there
   after. At Yizkor, we recite a prayer that we remember our loved ones.
   That we pledge Tzedakah (righteousness and not necessarily charity) to
   their memory. We ask that G-d keep our loved ones under the wings of
   his Divine Heavenly Presence.