Survival aspects will be one of the most important mechanics in Fallout 76. You will need to provide your character with food and water. These supplies will probably be collected through exploration. This won't be easy because edible food will be in limited quantities. Also, food will get spoiled over time.
During your playthrough you will have to provide your character with food and water constantly. This will be hard to do due to radiation that causes mutations. These mutations will have impact on your appearance, buffs and debuffs. You will probably be able to heal yourself with medicaments.
Fallout 76 will feature crafting system. Thanks to that you will be able to craft weapons, armor, ammo and food. The majority of the items will require blueprints and recipes. Every crafted item can be shared with other players.
Also, the developers assure that pieces of equipment will worn out. You will have to repair them.
Fallout 76 is an online game which means that you will face other players. However, doing that may not be a good idea - you will get bad reputation on the server. It is better to trade with them - by doing that you can get valuable resources.
Besides other players, you will also face numerous beasts. Your character leaves the Vault after only 25 years since the end of the Great War - the radiation is still present and it has impact on the world. This makes the animals change, evolve, grow - you can encounter giant sloths, two-headed opossums or intelligent plants.
The game will lack raiders. Instead, players will face a faction called Scorched - half-ghouls who can use firearms.
In Fallout 76 you will be able to create your own mobile base called C.A.M.P. You can build it anywhere, excluding areas around the titular Vault 76. If two players decide to have a base in the same location, one of them will either have to leave and find another spot or die.
C.A.M.P. allows players to upgrade their weapons, craft ammo, eat or rest. It is also probable that you will be able to leave your gear there without a fear of others stealing your items.