The Himalayan Mountains
Being the youngest mountains in the world, the Himalayas are categorized as folded mountains. They spread along the northern border of India forming an arc which of about 2400 km varying in width from abotu 150~400km.
The Northern Plain
Formed by three river systems: the Indus, the Ganga and the Brahmaputra this plain is composed of an extremely good alluvial soil. It's characteristic is the time it had been deposit which goes in millions of years.
The Peninsular Plateau
A tableland which is mainly made by rocks. They seem to be the oldest of rock as it is supposed that they were formed from a part of the Gondwana land which drifted away. Features characteristic for the plateau are broad and shallow valleys and rounded hills.
The Indian Desert
It is situated around the western margins of the Aravali Hills. The rainfall in the regions is merely about150 mm a year and so the vegetation is scanty at best. The only significatn river in the area is called Luni. Barchans are a characteristic part of the scenery there
It's important to not that the Islands around India are really diverse in terms of flora and fauna. It's good to mention the biggest archipelagos - Lakshadweep as well as Andaman & Nicobar Islands.