The word samskāra, in a technical sense, means a ritualistic act (accompanied by appropriate mantras) by which a person is rid of his defects and limitations, and made refined by adding some specialty. Such samskarās (sacraments) as listed in the smriṫis and dharma śhāstrās vary from 16 to 40. However, the 16 samskārās-generally called shoḍaśa- samskāras (sixteen sacraments) have been widely accepted. These sixteen sacraments start from the time of conception to the time of death with its rites being the last sacrament.
Hindu scriptures do not consider birth as the starting point of life. It goes farther back, as it is conditioned by heredity, parentage and environment. Keeping this in mind, the samskāras start first with conception. The sixteen sacraments are: 1) Garbhādāna (attaining the wealth of the womb and intent to have a child), 2) Pumsavana (quickening the fetus), 3) Sīmantonnayana (baby shower), 4) Jātaka Karma (child birth ceremony), 5) Nāmakaraṇam (naming the baby ritual), 6) Nishkramaṇa (baby's first outing), 7) Annaprāsana (baby's first solid food), 8) Ćūdakarma (baby's first hair cut), 9) Upanayanam (thread ceremony), 10 to 13) Vedavratās (Vedic rituals), 14) Samavartana (end of formal education), 15) Vivāha (marriage ritual), 16) Anṫyeshṭi (cremating ritual). In later dharmaśāsṫra literature, the four Vedavratās were omitted and the following four were added- Karṇavedha (piercing the ear-lobes); vidyārambha (same as aksharābhyāsa, learning the alphabet); vedārambha (first study of the Vedas); keśānta (cutting the hair or shaving the beard).
Saṁskārās like upanayanam are performed only in certain varṇās, in this case brāhmaṇa. The actual meaning of upanayanam is to take the person to the guru (teacher). The saṁskārās help to purify our mind, refine our attitudes and prepare us to achieve the ultimate life goal of mokṣha (liberation). It's like climbing steps to reach the top, every little bit helps and we cannot reach high without climbing one step at a time. The ancient sages always kept the common man in mind and showed equanimity towards humanity and worked very hard with strict observations.
The land which has provided sacraments for our spiritual progress is none other than our 'Susaṁskāra Bhūmi'.