Indian Administrative Service (IAS) 
The IAS Officers handle affairs of the government. At the central level, this involves the framing and implementation of policy. They also represent the government in other countries and in International forums. They are even authorised to sign agreements on behalf of the government. At the district level, it is concerned with district affairs, including development functions. At the divisional level, the IAS officers look after law and order, general administration and development work. In IAS cadre you can be sub-magistrate, district magistrate, joint secretary, deputy secretary etc.

Indian Police Service (IPS)
The IPS (Indian Police Service) is responsible for public safety and security. The IPS mainly takes care of law and order, which, at the district level, is a responsibility shared with the IAS; crime prevention and detection ; and traffic control and accident prevention and management. On completion of probation an IPS officer, begins his career as a Assistant Superintendent of Police of a sub-division. The Police service is divided into various departments like Crime Branch, Criminal Investigation Department (CID), Home Guards, Traffic Bureau.
They also offer there services to Central Policing Agencies like the Intelligence Bureau (IB), Central Bureau of Investigation (CBI), Cabinet Secretariat Security, the Border Security Force (BSF), and the Central Reserve Police Force (CRPF).

Indian Forest Service (IFtS) 
Indian Forest Service was established for the efficient administration of the country's forest reserves. This is a challenging career as you will be responsible for the conservation and management of forest resources. 
Central Services

Indian Foreign Service (IFS)
The Indian Foreign Service deals with the country's external affairs, including diplomacy, trade and cultural relations. It is responsible for the administration and activities of Indian missions abroad, and for the framing and implementation of the Government's foreign policy. Probationers at first work at the External Affairs Ministry, then they are posted to the Indian Mission of a particular country, as third secretaries. 

Indian Railway Service
It is essentially responsible for the running of India's vast railway network. There are four non-technical and technical or engineering cadres in the railways. Entry for non-technical services - the Indian Railway Traffic Services (IRTS)- responsible for freight, passengers and movement of trains, the Indian Railway Personnel Services (IRPS)- responsible for recruitment and administration of staff, the Indian Railway Accounts Services (IRAS)- responsible for maintenance of accounts, and the Railway Police Service (RPS)- responsible for providing security to railway properties such as railway tracks, personnel, equipment etcis through the Civil Services examination. However, the engineering services (IRSE) have a different recruitment procedure. 

Indian Postal Service
Responsible for the efficient functioning of the postal and telegraph services, officers after training with field officers are appointed as Senior Superintendent of Post Offices, Assistant Post Master General through out the country and also in the Ministry at the centre.

Indian Customs and Central Excise Service
The Indian Customs and Central Excise Service (IC&CES) is basically concerned with two main aspects, mainly Customs and Excise. While Customs is concerned with the checking and levy of duty on taxable goods brought into the country, the Excise department is involved with the taxation of goods manufactured within the country. 

Audit & Accounts Service
Indian Audit & Accounts Service comes under the Controller and Auditor General of India (CAG) which is responsible for the maintenance and audit of accounts in the states, as well as Union and State Governments. These officers work in the audit offices under CAG and in central ministries and state governments. 
Indian Defence Accounts Service (IDAS) is responsible for maintaining and auditing of accounts of the defence services
Indian civil Accounts Service (ICAS) under the control of Secretary (Expenditure), Ministry of Finance, maintains accounts of the State, Central governments and public sector enterprises. 

Indian Information Service (IIS)
IIS under the Ministry of Information and Broadcasting, is responsible for running government owned broadcasting and advertising agencies like All India Radio, Doordarshan and DAVP. The service is also responsible for handling press and public relations for the various central ministries, public sector enterprises and defense forces at home as well as abroad. 

Indian Revenue Service (IRS)
IRS is responsible for fixing, assessment and collection of income tax. The service also has specialized branches dealing with the investigation of tax evasion, statistics and so on.