The preliminary examination in the UPSC selection process is crucial as it serves as a qualifying test that screens candidates for the main examination. It consists of two objective-type papers assessing general studies and aptitude, and only those who secure the minimum qualifying marks are eligible to proceed. This stage helps the commission filter candidates based on their general awareness and reasoning abilities. Thus, performing well in the prelims is essential, as it directly determines the aspirant's continuity in the civil services examination process.