A nuclear winter has occured and the Vault dwellers survived. You are one of them - welcome to the wasteland.
Your journey begins with you searching for the water chip. You technically can beat the game at level four, but its not really fun if you do just the bare minimum. If you truly explore the game and use the free roaming available to you the game can take you anywhere from 2 to 40+ hours of game play, but thats assuming you truly want to explore and do everything. Otherwise you can expect probably about 10 to 20 hours of gameplay.
Fallout will leave you with a sense of awe, wonder and amazement. You will start asking yourself questions such as what secrets does the Glow hold? What happens if I do this differently, and of course, why don't I just kill everything?