HELLO SHABARISH
SInce you did not mention your college in your question but according to the tags you may be talking about IIT Madras.
it is one of the 1-tier engineering college of india and to grab a seat you should appear two entrance exam
1. JEE MAINS
2, JEE ADVANCED
to know more about this exams refer this link
JEE MAINS https://engineering.careers360.com/exams/jee-main
JEE ADVANCED https://engineering.careers360.com/exams/jee-advanced
HOPE IT HELPS!!

Yes the admission is based on the Entrance exam, the admission for B Tech is based on JEE Advance which is a two stage examination , first JEE MAIN followed by JEE advance, for M tech admission is based on GATE and for M Sc admission is based on JAM

Please follow the links for more details on specific entrance exam

JEE ADVANCE

https://engineering.careers360.com/exams/jee-advanced

GATE

https://engineering.careers360.com/exams/gate

JAM

https://university.careers360.com/articles/jam