Please explain me what is bitcoin I need to know more about a bitcoin because my friend told me so much informations but I need more because I want know  everything.

Maybe this forum looks so great ,maybe bitcoin can replace every fiat money we will se that later.I heard a lot about a bitcoin and my friend told me that bitcoin will is best virtual money but I am not sure can I trust him?

It looks really nice but for what we can use that paper picture money,is it like a picture or we can use it to pay something.Maybe I shoud buy it and maybe I can sell later to somebody for more money.