Bihar is primarily located in the fertile:

Gangetic Plains
Deccan Plateau
Thar Desert
Himalayan foothills

Bihar is primarily located in the fertile Gangetic Plains. The Gangetic Plains are a vast, fertile plain in northern India that is home to over 400 million people. The plains are formed by the Ganges River, which is one of the longest rivers in the world. The Ganges River is a major source of water for irrigation and drinking water in India. The Gangetic Plains are also home to a number of important cities, including Delhi, Agra, and Varanasi.

The Deccan Plateau is a large, plateau region in central and southern India. The plateau is made up of a number of different rock types, including granite, basalt, and sandstone. The Deccan Plateau is a relatively dry region, with an average annual rainfall of less than 1000 mm. The plateau is home to a number of different ecosystems, including forests, grasslands, and deserts.

The Thar Desert is a large, desert region in northwestern India. The desert is located in the state of Rajasthan. The Thar Desert is the hottest desert in India, with an average annual temperature of 30 degrees Celsius. The desert is home to a number of different plant and animal species, including camels, snakes, and scorpions.

The Himalayan foothills are a region of mountains and foothills that lie at the foot of the Himalayas. The foothills are located in the states of Uttarakhand, Himachal Pradesh, and Jammu and Kashmir. The foothills are a popular tourist destination, due to their beautiful scenery and their proximity to the Himalayas.

In conclusion, Bihar is primarily located in the fertile Gangetic Plains. The Gangetic Plains are a vast, fertile plain in northern India that is home to over 400 million people. The plains are formed by the Ganges River, which is one of the longest rivers in the world. The Ganges River is a major source of water for irrigation and drinking water in India. The Gangetic Plains are also home to a number of important cities, including Delhi, Agra, and Varanasi.