With the update you'll be able to browse mods from within the game, while the new "creation kit" will let you create everything from new quests to new weapons using a new in-game suite of tools. "Our goal was to make mods easier and more accessible than ever before, for both the creators and the players," the developer says.
While mods previously existed in the PC version of the game, the update opens them up to everyone. Today developer Bethesda released an open beta for modding in the PC version of the post-apocalyptic RPG. Mods are now officially supported in Fallout 4.