The full form of UPSC is the Union Public Service Commission. It is a constitutional body in India that is responsible for conducting various examinations and selecting candidates for recruitment into various civil services of the government.

Establishment and Composition:
The UPSC was established on 1st October 1926 as a Public Service Commission and later renamed as the Union Public Service Commission on 26th January 1950. It is a central agency that functions independently under the Ministry of Personnel, Public Grievances, and Pensions.

The commission consists of a Chairman and ten members who are appointed by the President of India. The Chairman and members hold office for a term of six years or until they attain the age of 65 years, whichever is earlier. They are appointed based on their qualifications and experience in various fields such as administration, law, education, etc.

Functions and Responsibilities:
1. Conducting Examinations: The UPSC is primarily responsible for conducting the Civil Services Examination, which is considered one of the toughest competitive exams in India. It also conducts various other examinations like the Indian Forest Service Examination, Engineering Services Examination, Combined Medical Services Examination, etc.

2. Recruitment: The commission selects candidates for appointment to various civil services in the government, including the Indian Administrative Service (IAS), Indian Police Service (IPS), Indian Foreign Service (IFS), and other Group A and Group B services.

3. Advising the Government: The UPSC advises the government on matters related to recruitment, promotion, and disciplinary cases concerning civil servants. It also assists in framing and amending recruitment rules, service conditions, etc.

4. Conducting Interviews: The commission conducts interviews for the final selection of candidates who have qualified the written examinations. The interview panel consists of experts from various fields who assess the candidates' personality, knowledge, and suitability for the respective services.

5. Constitutional Duties: The UPSC has the responsibility of conducting examinations for appointments to the services of the Union and the All-India Services. It is also consulted on matters related to the appointment, transfer, and promotion of civil servants.

6. Training and Development: The commission organizes training programs and workshops for civil servants to enhance their skills and knowledge. It also conducts research and studies on various aspects of administration and governance.

Conclusion:
The UPSC plays a crucial role in the recruitment and selection of candidates for various civil services in India. It ensures transparency, fairness, and meritocracy in the selection process, thereby maintaining the integrity and efficiency of the civil services.