Feats in Underrail are similar to perks or traits in other RPGs. They are permament elaborations of your character and serve the purpose to further customize your character build with unique active abilities, skill boosts or passive abilities. Feats do not boost Base Abilities, but characters gain a base ability point every fourth level.
For every even level in Underrail, you gain a feat point. New characters start with two feat points. Base ability and skill requirements of feats check your unmodified base/skill scores, not effective scores that include bonuses.
In order to finalize your level up phase or complete character creation, you must spend all points including all feat points. You cannot save feat points for later use and you cannot remove or reallocate them once level up phase has been finalized.
Some feats cannot be purchased with feat points when leveling up, instead they require training or other means of acquiring outside leveling. One such feat is Psi Empathy. Names of these feats have different color in the feat description panel. In older versions prior to 1.1.0, these were marked with (requires training) on the feat list before training them, or (Trained) once trained.
Characters that have leveled past level 25 become a veteran. In addition to regular feats, veteran characters can pick feats from new veteran feat pool. Names of these feats have different color in the feat description panel and their icons have similar color elements. Veteran feats, at least in Underrail: Expedition, tend to be more general in nature, but they can also give your character some important bonuses that you cannot otherwise obtain. First examples of veteran feats were showcased in Dev Log #48: Veteran Levels.
In Underrail: Expedition, player characters also gain a specialization point each level after 15, up to total 15 specialization points at level 30. These specialization points are used to further improve normal feats, often across a specific dimension. Like veteran feats, specializations will not be available nor visible to characters without the Expedition DLC. For more details, see Dev Log #54: Specialization and Veteran Level Changes.