Smite

Smite is a category of unique weapon attacks that, unlike normal attacks which generally only cost an Action, additionally expend Spell Slots (and often a Bonus action) in order to activate. Though requiring a spell slot to initially activate, they do not consume the spell slot on a miss. As they are considered weapon attacks they can trigger and be used with  Extra Attack, and in the case of  Divine Smite can be used multiple times per turn. The damage they deal is also subject to modification caused by a critical hit.

List of Smite abilities

•  Banishing Smite 
•  Branding Smite
•  Blinding Smite
•  Divine Smite
•  Searing Smite 
•  Thunderous Smite
•  Wrathful Smite 
•  Lunar Smite  (NPC-exclusive)
•  Staggering Smite  (NPC-exclusive)

Notably, Divine Smite functions slightly differently from the other smites. Here are the key differences.

Divine Smite

Despite consuming spell slots, Divine Smite is not a spell and does not interact with any effect or ability that only works with spells. Examples include  Counterspell, Vivacious Cloak, or  Tempestuous Magic. Unlike other smite spells, Divine Smite can also be configured to trigger automatically on a hit or critical hit via the Reactions menu. See  Divine Smite (reaction). This allows you to use Divine Smite on any melee weapon attack and multiple times per turn, even while dual-wielding. When triggered in this way, the only additional resource consumed is the selected level of spell slot.

• Divine Smite cannot be triggered by ranged attacks.
• Divine Smite can be triggered as a reaction when using other smites, allowing for two different smites in a single attack.
• Despite being configured in the Reactions menu, Divine Smite never consumes the Reaction resource.

Other Smites

Other smites cannot be triggered as reactions and must be used manually; however, Divine Smite can be triggered as a reaction when using other smite spells allowing for two different smites in a single attack. Other smites also count as proper spells for the purposes of features like Ring of Elemental Infusion or  Empowered Evocation, and will interact with effects such as these, including the possibility of being affected by Counterspell.