Bitcoin is a virtual currency meaning it does not exist physically but in digital form. It is based on the concept of blockchain which is an amazing technology. You can buy bitcoins via fiat currencies and trade them through cryptocurrency exchanges. Since it is a very volatile currency you have high chances of making profits but also equally high chances of incurring losses, so Id suggest you do a thorough background research on this topic before venturing into the world of Bitcoins or for that matter any other cryptocurrency. Best of luck! 