Enneracts in Wolcen: Lords of Mayhem this is how you unlock new skills. Because the game is classless, allowing you to learn any type of spell or skill you find, Enneracts are a fairly common drop. You can get them from dead enemies, chests or corpses that you can find all over the game. The eneracts appear in your inventory in the form of small books, and to learn them, you just have to click on them with the button mouse right in the inventory screen.
All Enneracts will tell you what types of weapons they need to be used. Some are only melee, while others require bows or pistols. Some can only be used with catalysts and staves, traditional weapons for wizarding wizards. If you don't plan on using a particular spell or finding a duplicate Enneract, you can sell them to Demetra at Stormfall for Primordial Affinity, which can be used to upgrade skills learned.
Demetra will also sell you different Enneracts at different times during the campaign, so it's always a good idea to check what she has in stock. She may have a few highly wanted Enneracts in stock, and if you haven't had any luck with RNG, this is a great way to get some new skills for your build.
Skills can be improved when using in combat or by using the Primal Affinity you can get from Demetra. How you want to play the game will dictate how you use Enneracts. If you plan to stick with one build type, you can just sell the Enneracts that you can't use with the weapons of your choice. If you want to keep your options open, it's a good idea to keep the Enneracts in your storage vault, so you can decide what to do with them later.