In Fallout 76, there will be a "premium currency" called Atoms. According to Bethesda Marketing Exec Pete Hines, Atoms can be spent by the player in exchange for new outfits and skins. The game company has been clear to say that the items you purchase with Atoms are entirely cosmetic and do not affect gameplay.
You can earn Atoms in two different ways: with gameplay and real life money. You will have the option to purchase additional Atoms for your character using a real-life money microtransaction. The exact dollar-to-Atom rate has not been disclosed at this time. Otherwise, you are awarded Atoms for completing various challenges or goals. While many are concerned that this method will yield an unrealistically small number of Atoms, Hines reassures us that it is not the case.
"Atoms are things that we use and hand out as you play the game--quite honestly we throw them at you all the time. You get them as little rewards leaving the Vault or the first time you kill a creature or the first time you pick fruits or vegetables from somewhere. It's a little challenge reward. Atoms are used in our shop to buy cosmetics things. So you know, new outfits or skins or things like that. [Things to customize] your character to look unique from everybody else."
Examples of this can be seen in recent screenshots, where players earn 20 Atoms simply for leaving the vault.
It's also been stated that anyone who preorders Fallout 76 on the Xbox One will be awarded 500 Atoms at the start. Since we still don't know how much Atoms are worth, it's not clear how beneficial this deal is.
Lately, Atoms will not be available for purchase during the Break It Early Test Application. It is presumed that players can still earn the currency through gameplay during this time, though it's not explicitly stated.