Feats are special features that either give a character a new capability, or improve one that he or she already has. They are more like innate abilities than skills, and as such, have no ranks or progression. A character either has the feat or not. As with skills, there are a wide array of feats in Neverwinter Nights, and no character will be able to choose them all.
Feat selection (when applicable) occurs towards the end of the level-up process. (For many classes, this is the last step of leveling.) The game automatically filters the list of feats, presenting a list of just those that can be selected. In the event that multiple feats can be selected, the choices for each are merged into one list, and the feats can be selected in any order. With each feat selected, the list of choices is re-filtered for those that can be selected alongside the just-made selection. (This can include both removing one set of choices from the merged list, and adding feats whose prerequisites were just met by that feat selection.) A selection can be undone before accepting it, with the list of feat choices again automatically adjusting.
Once gained via level-up, the only way a feat can be removed is through an experience point loss that results in losing the level during which the feat was chosen. Feats gained during character creation (or during creature creation in the Toolset) can never be removed. (This is in contrast to feats gained solely via an item property, as those feats naturally are lost when the item(s) with the property is unequipped. Feats granted by spells or polymorphs are implemented as item properties.)
Many of the feats in the game are "automatic", meaning they apply with no effort required on the player's part. Others are "selected", meaning they apply when the player selects them. Selection is typically done either by right-clicking the feat's target and finding the feat in the radial menu, or by assigning the feat to a quickslot then activating the quickslot and clicking the target. These feats are often found in the radial menu under one or more of the player's classes in the "Special Abilities" subradial (leftmost option), but some are found under "Special Attacks" (lower-right option).
A special case of the "selected" feats are the combat modes. These feats act as a toggle on the PC (so do not require a target if activated from the quickbar). Combat modes are typically found under "Special Attacks" in the radial menu, with the exception of flurry of blows, which is under the monk abilities under "Special Abilities". Another special case of "selected" is "cast", indicating the feat can be found under the "Cast Spell" subradial (upper-right option). This use is specific to the epic spells.
The metamagic feats are different than both "automatic" and "selected" in that they apply when a spellcaster chooses a spell to prepare or cast. Instead of directly selecting the feat, the caster chooses a spell modified by the feat (if such a selection is available). Item creation feats are also special in their method of selection. Using an item creation feat entails casting a spell on an appropriate item, e.g. a blank scroll for scribe scroll.
Feats are acquired both through a regular process that is the same for every character (general feats), and as bonuses dependent upon the choices made for each character.
General feats are chosen as a character gains levels. The first general feat is chosen at character creation, and an additional one is gained every three character levels (levels 3, 6, 9, 12, etc.). Some of these feats have prerequisites that must be met before selecting them. These are perhaps the most commonly referred-to type of feat.
Bonus feats are granted to a character based upon race or class level. Many of these feats are predetermined, simply gained at the specified time. Others provide players a choice as to which feat to gain and are treated similarly to general feats in terms of that selection. In the former case, any feat prerequisites are ignored, but not so in the latter case. (For example, a monk gains cleave at level 1, even if the monk lacks power attack and a strength of 13. A fighter, however, has a choice of cleave or several other feats, so the fighter must have the prerequisite power attack and strength of 13 to select cleave.) Most racial bonus feats are predetermined (the exception is the human bonus feat), as are most pre-epic class bonus feats. All epic classes offer bonus feats selected from a list of choices, offered at regular intervals (every 2, 3, 4, or 5 class levels, depending on the class).
Epic feats become available for selection when a character becomes epic (character level over 20; requires the Hordes of the Underdark expansion). Some epic feats expand upon existing feats (such as epic weapon focus improving weapon focus), while others provide options far beyond what a character could accomplish pre-epic. These feats supplement the existing feat choices, both for general and bonus feats. These feats merely supplement; they do not replace. (In one sense, epic feats are nothing more than feats with a prerequisite of "character level 21".) An "epic bonus feat" is best read as an "epic bonus" feat, as it is the bonus that is epic, not necessarily the feat.