Final answer:
A tribe is a social group in decentralized societies with a headman, united by kinship or religion, and focused on alliances among kin groups, contrasting with centralized chiefdoms.
Step-by-step explanation:
The type of social group you are asking about is often found in decentralized societies and is referred to as a tribe. Tribes generally consist of hundreds of members united by factors such as shared religion, kinship, and cultural practices with a headman leading the group. Decisions within such groups are centered on making and breaking alliances between different kin groups, and often involve extended family structures or councils that facilitate leadership and conflict resolution. Political power within tribes is not centralized, but rather distributed among the kinship groups, and leaders hold persuasive authority without formal enforcement power.\\
These communities may engage in subsistence practices like pastoralism or horticulture, with extended families controlling resources. This structure contrasts with societies organized under a chiefdom, where a chief holds centralized economic, political, religious, and military power. Despite the diversity of political organizations worldwide, tribes and chiefdoms represent different points on the spectrum of political structure varying from shared to centralized power respectively.