The Prime Minister's Office (PMO) in India is an essential institution in supporting the Prime Minister and the Cabinet in their duties of running the country. The functions of the PMO in the governance of India are as follows:

• Policy Development and Coordination: The PMO is responsible for formulating policies and supervising their implantation across various Ministries. It acts as an intermediary between various Ministries and the Prime Minister.
• Decision Making: The PMO plays a critical role in providing Cabinet with relevant and accurate information on policy issues and the possible outcomes of various decisions.
• Communication Management: The PMO also handles the communication between the Prime Minister and the Cabinet. It also directs the government's public communication strategy.
• Administrative Support: The PMO provides general administrative support to the Prime Minister and Cabinet, including dealing with personnel matters and official protocols.
• International Relations: The PMO plays an important role in managing India's international relations, engaging with important international actors, and coordinating the Government's international policies.
• Crisis Management: The PMO is responsible for handling crisis and emergency situations like natural disasters, terrorist attacks, etc.

Thus, as the backbone of the Indian government, the PMO plays a crucial role in the governance of India.