Meghalaya is dominated by three principal groups of people. The Garo in the east and west Garo hills, the Khasi-Pnar in the east and west Khasi hills and the Jaintia hills. They follow primarily a matrilineal system. The Khasi group belongs to the Mon-Khemar sub-family of the Austro group of people. The Garo group is a part of the greater Bodo Kacheri family both by ethnic group and language. Their present location enabled them to maintain many of their traits and characteristics.

The Khasi-Pnar group indicated two prominent sub-groups of the Khasi and the Pnar. The former occupied the central highlands or the Khasi hills and the latter towards east, the Jaintia hills. The groups living in the northern and southern part of the main central highland, section were known by the terms of 'The Bhoi and War'. They are divided into number of clans and are essentially differentiated from each other by their location and function they perform. 

Within the four districts of the combined Khasi and Jaintia hills there are number of dialects. Based on the dialects, the community is generally divided into five groups namely the Khasis of the central plateau, the Pnars or Jaintia in the east, the Wars in the south, the Lyngams in the west and the Bhois in the north.

The Meghalaya plateau is inhabited by three dominant tribes. These are: 

1.       The Garos in the western section of the plateau

2.       The Khasis in the central section of the plateau

3.       The Jaintia in the eastern section of the plateau

Garos

The Garos call themselves Achiks. 'Garo' is believed to have been derived from the name of one section of the tribe who are found in a compact area in the middle of the districts southern belt. The Garo tradition speaks of their migration from Tibet.

In course of time, the Garos society was divided into three major exogamous, 'Kin-groups' or Katchis, namely Marak, Sangma and Momin. These are further sub-divided into such groups as Areng, Shirra and Ebang.

Marriage between members of the same Katchi is totally prohibited by tribal law. Each of these Kin-groups is further sub-divided into a number of lineages called Machong. The Machong with its component households is the basic unit in the Garo social organization. A Garo belong to his particular Machong from his birth. In each village, the dominant Machong selects the headman who is Nok-ma literally means house-mother. Usually Nok-ma would be a man.

Inheritance among the Garos is restricted to the female line. Each family selects an heiress (nok-ma). A couple with no children may adopt the daughter of the wife's sister as heiress. The heiress is usually linked in marriage with the son of the father's sister.

The institution of the 'Bachelors Dormitory' (Nok-pante) is found only among the Garos. All unmarried young men and growing boys must live in the dormitory. These young people carry out allotted tasks entrusted to them by the village elders.

The Garo tribal groups consists of sub-tribes . They are 

(a) Ambeng (in the western part including Tura)

(b) Atong (in the lower Simsang valley)

(c) Akawa (north-eastern parts and extend upto Goalpara and Kamrup in Assam)

(d) Matchi (upper reaches of Simsang valley)

(e) Chibok (upper Bhugi valley)

(f) Ruga (lower Bhugi valley)

(g) Dual (upper Simsang valley)

(h) Chisak (north of Matchi and Dual in central highlands)

(j) Kotchu (eastern parts)

(k) Koch (south-western parts)

Besides these, there are others like Megamo in the mid-western parts and the Dikos.