Holy

Holy is an attribute of objects, energies or characters. Holiness is most closely associated with Light but is not exclusive to it. Holiness comes with a connotation (but not a guarantee) of purity, healing, sinlessness, benevolence, order, and the favour by the divine.

Some attacks will count as holy, and thus have the Holy modifier. In the stat system, they will typically deal 50 extra damage compared to a mundane version of the same attack, increased to 100 extra damage against Unholy enemies. For example, a splash of normal water to someone's face probably does 0 damage if there isn't a lot of force. Holy water which is intended as a weapon will cause some minor searing from holy judgement of sins, dealing 50 damage. Use it against a vampire or demon, and it will sear harder, dealing 100 damage! Remember that some characters may have more weaknesses or take even more damage from holy energy, though this is on the part of the character's creator to determine. You might also choose to give your holy attack/ability more effects than just a damage increase compared to a modified version, including even more damage or effects against the unholy.

There are numerous creatures which count as innately holy. These include angels, slimes and faefolk.

Holy Magic
Holy magic is a group of spells which aren't restricted to any specific kinesis. Several of these abilities can be innately developed by holy beings, or learned through study by neutral races like humans. If you play tabletop RPGs like D&D, think of them as typically equivalent to cantrips or 1st-2nd level spells.
 * Projecting holy light. Not enough to do any sort of harm, except possibly against the unholy.
 * Cure Light Wounds, a healing spell. Quite weak in comparison to actual healing kinesis abilities, but it can help to soothe pain or mend that papercut you got while doing homework.
 * Blessing, applying a slight buff to a target.
 * Detecting when something is holy or unholy. (One wouldn't be able to tell specifics, like the exact species of something which seems visually totally human, or the particular powers of an item. Just able to identify the attribute.)
 * Courage, granting partial resistance to fear to oneself or one person.

On Player Use
Players may wish to use Holy abilities for any number of reasons, usually justified through a character's lore. Readers may get the impression that all players will tend toward making all their attacks Holy or Unholy since they're stronger than neutral versions of the same attack, but bear in mind that all such upgrades are opportunity costs. If you've gained an upgrade, you could use it to turn the fire you use for one of your attacks into angelfire, increasing its damage by 50, up to 100 against the Unholy. But you could also use that upgrade to instead just increase the temperature of the fire itself, increasing its damage by 75 against all enemies. And both of these have an opportunity cost compared to just increasing a character's durability or speed, or unlocking new abilities.

This is to say: just like for any other sort of power, don't feel pressure to use it for strength optimization purposes, since it's not necessary to make your character stronk. Opt for it only if you feel it fits your character.