The significance of the Civil Services (Preliminary) Examination in the UPSC process lies in its role as the first step in identifying eligible candidates for civil services. It tests general knowledge and aptitude, serving as a filtering mechanism for the Mains Examination. Approximately 10-15 times the number of vacancies are shortlisted for the next stage based on this exam, making it crucial for advancement. The Preliminary Examination not only assesses foundational knowledge but also helps build a candidate's analytical skills, creating a basis for more in-depth evaluation in subsequent stages.