The significance of the CSAT (Civil Services Aptitude Test) in the UPSC Preliminary Examination lies in its role in assessing candidates' general ability and decision-making skills. It serves as a vital screening tool, ensuring only those with the necessary aptitude progress to the Main Examination. The CSAT evaluates reasoning, comprehension, and analytical capabilities, which are essential for a civil servant. A strong performance in CSAT reflects the candidate's readiness for the demanding nature of administrative roles, making it crucial for success.