Hello student,
How to say you but actually have not mention that about which examination you are talking about. Actually after class 12th you can get admission into various types of colleges including engineering, Iti, medical nursing, diploma etc. But for each and every degree that entrance examination is different which you have to attempt after you 12th board examination or before. Often those examinations are for getting entrance in common general degree colleges also which is called as CET. CET is conducted by different colleges and different states. The entrance can be based of logical resoning English and the particular subject. Engineering examinations are based on physics chemistry mathematics, and medical examinations and based on physics chemistry and biology. Here I am providing your link you can go to this link below to know  more
https://learn.careers360.com