For playing backgammon online you first have to download the software, then register. Having done this you can start playing backgammon, for fun (Free Backgammon) or for Real Money, with players all over the world. You can play single games, session games or you can choose to play in tournaments.
Before playing backgammon for Real Money you have to deposit money into your account. After depositing the money you can join an existing table or create a new one. At the end the winner takes all the money and pays a small fee.
If you are a beginner you can start by backgammon for free. There is also a “Backgammon school” for those who want to learn how to play the game. That means you will have a tutor who will teach you how to play and will correct your mistakes.