I knew from the internet and heard it from my teacher,at first I did not know about this bitcoin.
One day I went to school and I was sitting alone, my teacher asked "Do you know about bitcoin?" I replied "I do not know sir" and by that time my teacher explained a bit about bitcoin and then I know what bitcoin is and I try to learn it on the internet.
At that time I was very curious about bitcoin and apparently bitcoin is very useful for my future.