I oftenly use Byju's in my spare time to get in depth concepts clear.They are one of the best in terms of teaching online.I mainly use them for Physics , Chemistry & Maths.They have a very unique style of teaching which I personally enjoy.Its easy to learn anything from home all you need is a good internet connection.
The faculty of Byju's is really good and there are many professional teachers who are passionate about teaching and so students enjoy and learn things quickly from them.
The main highlight of Byju's is that its not costly like the other online teaching sites who take a lot of money and offer less study material.
I personally suggest every student to try it once and I can guarantee that it would not be a waste of time.