Don't have Fallout 3 or Fallout New Vegas? We have descriptions of the two games right below!

Fallout 3 takes place in the year 2277, 36 years after the setting of Fallout 2 and 200 years after the nuclear apocalypse that devastated the game's world in a future where international conflicts culminated in a Sino-American war in the second half of the 21st century. The player character is an inhabitant of Vault 101, a survival shelter designed to protect up to 1000 humans from the nuclear fallout. When the player character's father disappears under mysterious circumstances, the player is forced to escape from the Vault and journey into the ruins of Washington D.C. to track him down. Along the way the player is assisted by a number of human survivors and must battle myriad enemies that inhabit the area now known as the "Capital Wasteland". The game has an attribute and combat system typical of an action strategy game but also incorporates elements of survival horror games.

Fallout: New Vegas takes place during the year 2281, four years after the events of Fallout 3, and 204 years after the Great War of 2077, making this installment chronologically the latest in the series thus far. The game is set in post-apocalyptic Las Vegas, Nevada, and the Mojave Desert, which is known as the "Mojave Wasteland." The Mojave Wasteland is roughly the same size as the "Capital Wasteland" in Fallout 3, and is spread across parts of real-world Nevada, Arizona and California. Unlike other cities in the Fallout series, Las Vegas was not struck directly by a nuclear attack. Its buildings remain intact, and mutation of its inhabitants is minimal.