UPSC is a Constitutional body. The constitution and functions of UPSC are delineated in Articles 315 to 323 of the Constitution of India. The functions of the UPSC are indicated below:
(1) It conducts examinations for the appointments to the services under union and all India services.
(2) It assists the States in framing and operating schemes of joint recruitment for any services for which candidates possessing special qualifications are required, in case requested by two or more states.
(3) It is to be consulted:-
(a) on all matters relating to methods of recruitment to civil services and for civil posts;
(b) on the principles to be followed in making appointments to civil services and posts and in making promotions and transfers from one service to another and on the suitability of candidates for such appointments, promotions or transfers;
(c) on all disciplinary matters affecting a person serving under the government in a civil capacity, including memorials or petitions relating to such matters;
(d) on any claim by or in respect of a person who is serving or has served under the government in a civil capacity, that any costs incurred by him in defending legal proceedings instituted against him in respect of acts done or purporting to be done in the execution of his duty should be paid out of the Consolidated Fund of India;
(e) on any claim for the award of a pension in respect of injuries sustained by a person while serving under the Government in a civil capacity, and any question as to the amount of any such award,
Also, it is the duty of UPSC to advise on any matter so referred to it by the President.
UPSC conducts various competitive examinations every year. Some of these examinations are Indian Civil Services Examination, Indian Forest Service Examination, Indian Statistical Service Examination, Geologists' Examination, Combined Defence Services Examination, National Defence Academy Examination, etc.
I think now you have understood that your question is not proper. You have to specify about which examination of UPSC you are talking.
Beware! I question everything and everybody.