The complexity of questions changes significantly from Prelims to Mains in UPSC. Prelims focus on objective-type questions that assess general awareness and basic understanding of subjects. Conversely, Mains presents descriptive questions that demand analytical reasoning, critical thinking, and articulate expression. This transition requires aspirants to not only understand topics but also synthesize ideas and present coherent arguments. The ability to delve deeply into subjects and express nuanced thoughts becomes vital in the Mains examination.