The correction window is a limited period provided by the National Testing Agency after the application process closes. During this period, candidates can modify certain details in their submitted JEE Main application form. The fields that can usually be corrected include personal information, academic details, exam city preferences, photograph, signature, and category information. However, not all fields may be editable, and the exact list of editable fields is specified in the official notification. Candidates must log in to the official website and make the necessary corrections before the deadline.