•The key backstory (United States vs. China, world apocalypse, Vaults, etc.)
•The most important characters (the player character, the Overseer - others are only relevant later in the game)
•The player's goals and objectives (search the surface world for a Water Chip and bring it back to Vault 13 within 150 days, in order to save the Vault)
•Movement (point and click)
•Interacting with the game world (right-click context menu, hotkeys, skill use)
•Inventory use (managing and equipping items, looting containers)
•Combat (turn-based system, melee attacks, ranged attacks, aimed attacks, action points, hit points, reloading)
•Different weapons (guns, unarmed, melee, etc.)
In a game where hand-holding is almost nonexistent, tutorial pop-ups everywhere would have killed the flow of the game and would have coddled the player, leaving him/her unprepared for later on… by making the player use his/her head, not only is there a genuine feeling of learning and progress, but the player now knows to expect little help when the game gets more difficult. By modern standards, this is sacrilege, but even today, getting into Fallout is fairly easy because of the way it's set up to encourage learning. Even if the player misses out on something right now, the player is almost guaranteed to learn the fundamentals.
Fifteen years later, the first Fallout still demonstrates effective teaching of both its narrative and gameplay through subtle gating, smart scenarios of vary scales which lead from one to another, and by giving the player increasingly challenging tests with a good feeling of progression and mastery. There might be a few rough edges, but for a game with so many moving parts, its opening accomplishes a lot without resorting to a single pop-up. Compared to contemporaries like Baldur's Gate, Fallout's opening still stands the test of time as a smart and effective piece of game design.