Trinity

Trinity is a special ability present in Kingdom Hearts, and to some extent in Kingdom Hearts: Chain of Memories and Kingdom Hearts II. While traveling between Worlds, Sora will occasionally come across a colored mark composed of three hearts connected by a circle, which causes the bottom command box to change to "Trinity". Activating this command will allow Sora, Donald, and Goofy to perform an action matching the mark's color. By using Trinity Marks, the party can open new paths or obtain rare treasures. There are a total of five different Trinity colors Sora, Donald, and Goofy can learn throughout the game.

As they are the main party and closest friends, the Trinity command will only appear if Sora, Donald, and Goofy are the party members; if another character, such as Aladdin or Ariel is in the party instead, the command will not activate.

Trinity marks are required to complete Jiminy's Journal and progress the storyline. Finding and activating all of them is not required to complete the game, nor to unlock the bonus ending movie. In addition, all Trinities can be returned to if they are missed at any point in the game.

Note: The only missable Trinity Mark is the red Trinity Charge mark in Oogie's Manor, as the manor itself disappears after defeating Oogie Boogie. This was fixed in Kingdom Hearts Final Mix, as the mark is instead located below an arch near the manor.

Trinity Jump
The first obtained in the game and by far the most common, this Trinity is learned after defeating the Guard Armor boss in Traverse Town. The blue marks represent the ability Trinity Jump; Sora, Donald and Goofy bounce on the floor, shaking treasure loose from somewhere above them, or accessing higher levels. Although this is the first mark to be learned, activating blue Trinities are not required to complete the game.

Trinity Charge
Second to be discovered, after sealing the Keyhole at Deep Jungle, the red marks are for Trinity Charge. Sora, Donald and Goofy will charge at a wall or barrier and break it, revealing a new path. Trinity Charge is required at some points in the game to progress the story, especially in Traverse Town.

Trinity Ladder
The third Trinity ability, green Trinity marks are activated after Agrabah is locked. They represent Trinity Ladder, where Sora, Donald, and Goofy climb on top of each other to reach something up high. The green Trinity is required at one point in Neverland; it must also be used to access the Moogle shop above Cid's store in Traverse Town and activate item synthesis.

Trinity Push
The fourth Trinity ability to be learned and the rarest of them with only a total of four in the game, yellow Trinity marks activate Trinity Push, allowing Sora, Donald and Goofy push a heavy object around. In order to obtain this mark, Sora must win the Phil Cup, Pegasus Cup, and Hercules Cup in Olympus Coliseum; he promptly puts it to good use by using it to reveal the Coliseum's Keyhole.

Trinity Detect
The fifth and final ability that Sora, Donald, and Goofy learn is Trinity Detect; the trio raise and point their weapons, summoning a treasure chest. It is learned after Riku is defeated for the first time in Hollow Bastion. This Trinity is not required to complete the game, but does net some useful things, especially the Lady Luck Keyblade and the Violetta staff for Donald.

Trinity Limit
The strongest Trinity ability is actually an attack, and consists of Sora creating an intricate Trinity mark on the ground and activating it with his Keyblade. It consumes all of the party's MP, but deals enough damage to wipe out any minor enemies within its area of effect, unless they are temporarily invulnerable, like the Shadow, Neoshadow, or Black Fungus.

List of Trinity Marks
  

Trivia

 * A Green Trinity symbol represents friend cards at the top left corner of the screen in Kingdom Hearts Re:Chain of Memories.
 * A White Trinity symbol appears next to "Button" during Trinity Limit in Kingdom Hearts II.