Hi Kaushik,
Hope you are doing well. The 10+2 examination certificate means your 10+2 marks card. The admit card cannot be termed as 10+2 certificate. It is an usual way of notation. Sometimes they will clearly mention the name name " marks card" and also sometimes they will mention as 10+2 certificate. It is usually called as certificate as it is a proof whether the marks that you have entered during registration is correct or not. I hope you got the point after reading this answer.

All the best.

Hello Kaushik,
10+2 exam is also called as class 12 or Pu2 exam in other states. After you complete class 10, class 12 result is important to get admission in engineering colleges. If you score above 90-95% you can get reduced fees and scholarships in several colleges. 10+2 result is your class 12 final examination result or marks card.