Hey,

NDA or National Defence Academy Exam is a national level exam organized by UPSC (Union Public Service Commission) to recruit candidates in Army, Navy and Air Force. It is a two-tier examination, wherein, candidates qualifying the written test will also have to clear the SSB interview round.

The eligibility is different for every post, applicants must fulfil the complete NDA Eligibility to apply for the exam.
Syllabus of NDA exam is based on CBSE 10+2 standards. The exam consists of 2 sections- Mathematics and General Ability Test.
Total duration of exam is 5 hours combinedly for both sections.The exam will be conducted in offline mode (pen and paper-based).Candidates successfully qualifying the written test would be shortlisted for NDA Selection Process
Candidates qualify the written test are called for NDA SSB Interview. Final selection is done on the basis of overall performance of the candidate.

Hope this helps.