What do you understand by mahajanapad

The Mahājanapadas were sixteen kingdoms or oligarchic republics that existed in Northern ancient India from the sixth to fourth centuries BCE during the second urbanisation period.

Mahajanapadas literally "great kingdoms" refers to 16 monarchies and 'republics' that stretched across the Indo-Gangetic plains from modern-day Afghanistan to Bangladesh in the sixth century B.C.E., prior to and during the rise of Buddhism in India. They represent a transition from a semi-nomadic tribal society to an agrarian-based society with a vast network of trade and a highly-organized political structure. Many of these “kingdoms” functioned as republics governed by a general assembly and a council of elders led by an elected “king consul.” The Mahajanapadas are the historical context of the Sanskrit epics, such as the Mahabharata and the Ramayana as well as Puranic literature (the itihasa). They were also the political and social context in which Buddhism and Jainism emerged and developed.

Most of the historical details about the Mahajanapadas are culled from Sanskrit literature. Buddhist and Jaina texts refer to the Mahajanapadas only incidentally. In a struggle for supremacy during the fifth century B.C.E., the growing state of Magadha emerged as the most predominant power in ancient India, annexing several of the Janapadas. They were all eventually absorbed into the the Maurya Empire after 321 B.C.E.