The Samskaras

According to the Manusmirti the sacraments or rites of transformation "for" twice-born "- that is, for those in the first three castes (Brahmins, Kshatriyas and vaisya) - are twelve, according other texts they are sixteen, and they mark an important moment, a passage in the life for Hinduism.
Let's look at what are the sixteen necessary samskaras, those that a good Hindu should celebrate, not forgetting that in reality there are parts of India or particular castes who celebrate more than fifty different sacraments and that those rites may also have different names.
The first samskara is Garbhadhana, the rite of conception or the infusion of the seed that should be celebrated before of  the conception to propitiate a good pregnancy and good birth.
The Pumsavana celebrates six months of pregnancy and is a ritual to have a boy.
In the fourth, sixth or eighth month (depending on the circumstances) of the first pregnancy is performed the samskara Simantonnayana:  the parting mother's hair.

The Jatakarman is the ritual of birth that is celebrated before the baby's umbilical cord is cut. With a spoonful of gold is given to the baby milk, honey and butter and you whispered in his ear, "vac" which in sanskrit means ‘word’. In this moment is given the secret name of the child, known only by the parents but the real name, the 'public' one will be given after (at least) ten days after birth in the fifth samskara named Namakarana.
The Niskramana literally means 'going out' and it is the ceremony performed after about four months after birth when the child first leaves home and meets the world and sees the sun.
By the seventh samskara, Annaprasana, the baby is ready to take solid foods and this moment  is celebrated at the sixth/seventh month. In sanskrit  'anna' means 'food'.
The Cuda or Cudakarana is cutting ceremony to be done, as appropriate, in the first or third year of a child's life.
Between the sixth and sixteenth month of birth (or later) is performed the Karnavedha, that the piercing of the lobe of the ears.

Vidyarambha, which literally means ‘beginning of knowledge’, can be considered as the first day of school when the child's life is no longer done only in games but also learning.
Very important is the Upanayana, which is the second birth for those born in the first three castes. In this ceremony the child is wearing for the first time the sacred thread Yagyopavit which is made of fiber varies according to the caste. At this time the boy is entrusted to a guru, a spiritual teacher who will introduce the study of sacred texts and make a boy an adult.
The rite Vedarambha is celebrated  at the beginning of the study of the sacred Vedas and the Upanishads.
The Kesanta - sixteen years - is a new shaving ritual.
The boy returns home after completing the period of study with the celebration of Samavartana. The boy became an adult.
The marriage is celebrated with the ritual of Vivaha and the funeral rites are Antyesti (last rites). In summary:

1.     Garbhadhana, literally ‘gifting the womb’ or ‘insemination’;

2.     Pumsavana, ‘producing a male child’

3.     Simantonnayana, ‘dividing the hair’ (of the mother);

4.     Jatakarman, ‘birth (jata) ceremony (karman)’;

5.     Namakarana, ‘rite (karana) of the name (nama);

6.     Niskramana, ‘going out’;

7.     Annaprasana ‘eating (prasana) food (anna);

8.     Cudakarana, ‘rite of  tuft or hair (cuda);

9.     Karnavedha, ‘ear (karna) boring’;

10.  Vidyarambha, ‘beginning (arambha) of knowledge or study (vidya)’;

11.  Upanayana, ‘introduction’ in the caste and in society;

12.  Vedarambha, ‘beginning (of study) of  Vedas’;

13.  Kesanta, ‘removing hair’;

14.  Samavartana, ‘returning (at home)’;

15.  Vivaha, ‘marriage’;

16.  Antyesti, ‘last (antya) sacrifice’.