Governance at Union Level
The Constitution of India has made alternate provision for the structure and functioning of all the three branches of the government - executive, legislature and judiciary, The President, the Council of Ministers with Prime Minister constitute the executive branch of the Government, the Parliament with its two houses - House of the People or Lok Sabha and Council of States or Rajya Sabha is the legislative branch and the Supreme Court heads the judicial branch.

President
The President is Head of the State. It is the highest public office in the country. All executive actions of the government of India are carried out in his or her name. The president is indirectly elected by an electoral college which consists of the elected members of both the houses of Parliament as well as State Legislative Assemblies including Union Territories of Delhi and Pudduchery.
Prime Minister
The Prime Minister is the most important functionary at the Central Government. The Prime Minster is appointed by the President, but the President has to invite only that person to be the Prime Minister, who is the leader of the majority party or coalition in the Lok Sabha.
Union Council of Ministers
The Ministers are appointed by the President on the recommendations of the Prime Minster. The Council of Ministers has three categories of Ministers - Cabinet Ministers, Ministers of State and Deputy Ministers.
Union Parliament
The legislative branch of the Union Government is called the Parliament which consists of the President and the two houses known as the House of the People (Lok Sabha) and the Council of States (Rajya Sabha). The House of the People is the lower house and the Council of States is the upper house.
Lok Sabha: The members of the Lok Sabha are directly elected by the people of India. The number of its members cannot exceed 550. Out of these, 530 are directly elected by the people of the States, and the remaining 20 members are elected from the Union Territories.
Rajya Sabha: The maximum number of members of this house cannot exceed 250. Out of these, 238 members represent the States and Union Territories and 12 members are nominated by the President of India.
The tenure of Lok Sabha is 5 years where as that of member of Rajya Sabha is 6 years. 1/3 members of Rajya Sabha retire every two years and new members are elected. The retiring members can be re-elected. It is a permanent house.
Supreme Court
India has a unified judiciary, wherein the Supreme Court is the Apex Court. Jurisdiction of the Supreme Court - Original Jurisdiction, Appellate Jurisdiction, and Advisory Jurisdiction.
As the interpreter of the Constitution, the Supreme Court has the power to protect and defend the Constitution. If any law or executive order is against the Constitution, the same can be declared unconstitutional or invalid by the Supreme Court.