Unlike previous Fallout games where it was mostly focused on single-player content, Bethesda is approaching Fallout 76 differently by making it a multiplayer game. In a way you could think of it like a combination of Fallout games and also Fallout Shelter, where you get the experience of Fallout but also the need to work together to survive the dangers of the wasteland.
Bethesda has since put out a little trailer video in which they explain how the multiplayer system will work. A quick note about the trailer: it has been recreated in the style of Fallout’s videos using cartoony characters to explain the multiplayer setup. It doesn’t actually show any in-game footage or dive into specifics.
However it does give players a rough idea of what they can expect during the course of the game, and why it is vital to group up with other players if they are hoping to make it through the game. It is an entertaining video and if you have a few minutes to spare, it could be worth taking a look at.
That being said, with Fallout 76 being a multiplayer game, Bethesda has acknowledged that players could potentially run into griefers, which is why they have been testing out a system that will help players deal with such players, and to potentially curb such behavior.