Hello Ishan, 

Percentile is a measure of your performance in a particular exam in comparison to other candidates appearing for the exam. It basically tells you about how many applicants have secured equal or less marks than you. This percentile is very important in JEE Mains as it helps in determining your rank, which in turn helps you to get admission in various engineering colleges across India. To predict your percentile and rank please refer to the careers360 link given below. 

https://engineering.careers360.com/jee-main-rank-predictor?utm_source=google-search&utm_medium=paid&utm_campaign=jeemain-rp

Hope this information was helpful.

Good luck.