I want to learn magento 2.Can anyone tell me what is best learning source including PDF,video,Online Tutorials.
Im not sure of any videos on M2 but the best place to start with Magento 2 - is to start with the development documentation.
And even then magento might seem a daunting task - if you have aren't familiar with magento already, i'd recommend looking into magento 1. Even though magento 2 is different, the database structure is the same and understanding the way magento uses blocks and xml to add these blocks is a great starting point.
You can also find more information on mage stores website, they seem to have a step by step on each section.
One of the best things you can do is get magento installed and play. Get stuck? ask a question or find a the question on here.
I will recommend this 12 hours course on Udemy. It teaches the core concept with real live project. https://www.udemy.com/simplified-magento-2-video-course-from-beginner-to-expert/ Disclaimer: I was part of the creator of the course.
After that, you can go for Magento study group. I found it quite useful https://u.magento.com/magento-2-certified-professional-developer