Engineering in India

This dilemma of reaching to a conclusion of choosing a branch is the one faced by a lot of students who appear for various engineering entrance exams. Engineering is nothing but making you visualize what goes on in the background when certain phenomenon happens and improvisation of such systems and if you don't have an eye for it, you might face a lot of difficulties in the branch you choose because all the branches in engineering are equally challenging.
And, one more thing, just in 12th standard you think that some area is interesting and you should choose it, then think of it and definitely consult your seniors.
Engineering courses are nothing like the perspective we have in the 12th standard. That might be a very little part of it.
For some core branches this information might be helpful:
Mechanical Engineers visualize the working of machines.
Electrical engineers work on the distribution of electricity in systems.
Information Technology is like subset of CS focused on application based study
Computer Science Engineering is the study of software and hardware
Petroleum Engineering is the study of hydrocarbons, extraction of the hydrocarbons and transferring them.
I think the most efficient way is to talk to a senior of the respective fields and explore the subject and find out if you are inclined.
Hope that Helps
All The best.