JEE Main

Offline test is basically a pen and paper examination. You get a printed question paper and depending on the examination you are given answer sheets or OMR sheets to bubble in the answers.
In online test each person is given a computer in the examination hall (A computer lab). Questions are displayed on the screen and most often you have to select radio buttons beside the options given. Online test has great advantages as you can see the entire question palette with the all the details like questions you have answered, marked for review etc. You can either view one question at a time or the entire question paper. From my experience viewing 1 at a time gives us more patience to solve it.
And most often Online tests are usually in 'Air-Conditioned' halls.
I would suggest you to go through online mock tests.

JEE Mains exam is one of the most popular & the toughest exams in India for engineering aspirants. Many students prepare for the exam every year to get admission in the dream college known as IITs and NITs. The JEE Mains cut-off was as follows:
General-81
OBC-49
SC-32
ST-27
You need a complete strategy and tips to crack JEE Mains exam.
Make a fixed schedule. Make a list of books and notes and study material you want to prepare from. Make a complete sight on the syllabus for exams mark the important topics and read them first and ask your teachers if you get any doubt, solve previous year questions, for practice stay positive and work by heart and don't waste a single minute from now.