Khan Academy is for those people who prefer knowledge over marks and if you want in-depth knowledge of your subject then khan academy is the way Khan Academy is free of cost and will explain you everything in detail. Khan Academy is one of the best place to find information online it has videos on every subject physics chemistry bio and maths and even some other subjects which cannot be found on other online sites don’t have. everything is explained in detail and you feel like you’re being taught live by a live tutor the one who studies by Khan Academy can never fall short of knowledge and will never need to cram anything as everything will be clear to him in depth.