Targeting is a game mechanic via effects to have a single fighter, unlike AoE, to go under the effects (sometimes none) of the effect. By clicking, you can select any fighter on the field, whether ally or enemy. Depending on the effect, targets can inflict a buff, a debuff, a lock, or an unlock.
Other card's effects can be triggered via target as well, known as the OnTarget trigger.
To give a better understanding, let's take a look at these two cards.
| About Robux Stack |
|---|
| Rarity: Colourless Token |
| Health/Power: Action |
| Effect: Inert when discarded. A target fighter gains 50 health. |
As you can see from its effect, Robux Stack is based on triggering another card's effect to gain benefits. Despite these types of targets having little effect on the boardstate in general, some decks use this to their advantage. One notable (but legacy) example is Santa Control, a deck using Plushie Santa and several targets to have control over the board with lifegain and random Rare fighters.
| About Kahgo |
|---|
| Rarity: Yellow Common |
| Health/Power: 200/300 |
| Effect: Whenever an effect targets this card: Give yourself a common card. |
Cards like Kahgo have an effect that can be triggered from target effects like Robux Stack. In this case, whenever Kahgo is targeted, you put a random Common card into your hand.
Some cards can only exclusively target enemy or allied fighters. Examples include SONICTHEHEDGEHOGXX.
| About SONICTHEHEDGEHOGXX |
|---|
| Rarity: Blue Epic |
| Health/Power: 600/300 |
| Effect: When this card is cast: Return target enemy fighter to its owner's hand. |