Key differences between the Civil Services Preliminary and Main Examinations include structure, purpose, and evaluation methods. The Preliminary Exam consists of objective-type questions aimed at screening candidates for the Main Exam, while the Main Examination employs descriptive questions to assess a candidate’s analytical skills and understanding of relevant subjects. The Prelims focus on general knowledge and aptitude, whereas the Mains delve deeper into specialized subjects chosen by candidates. Additionally, the Main Examination has a significant weight in the overall evaluation, alongside the personality test, making it critical for final selection.