You grow up in underground Vault 101 and set out after your father abruptly departs, stepping into a ruined Washington, D.C. region about two centuries after nuclear war. Super mutants, radiation and wild creatures make the surface dangerous, but the map is open, so you can follow the main story or wander toward quests and ruins of your own choosing.
Combat runs in real time, with the option to pause and target body parts using V.A.T.S., and your choices shape how characters treat you. The tone mixes bleak survival with dark humor. It is a single-player role-playing game for people who like exploring and building a character through a seven-attribute stat system.