Condition

Condition describes something that needs to be fulfilled before an effect can be activated. It can also describe when the effect activates.

Although Conditions, Costs and actions often have the same type (Continuous, Ignition, Trigger, etc) sometimes you need to mix them.

Types of Condition
Trigger - A condition that is checked when something happens or when a game state is reached (for example, the End Phase is entered, or a Spell card is activated). These conditions wait and listen for something to change.

Ignition - A condition that checks the game state when a player wants to activate an ignition effect (for example, "activate only if you control a monster")

Continuous - A condition that is constantly checking for changes in the game state. Use this if you think the condition could begin with "While..."

Inherent - Basically the same as Ignition, used only to be consistent with the Cost/Action types

Universal - Precludes Universal Costs/Actions. Use it wherever they are.

Modifiers
Or - When you have two conditions and an effect can take either of them... you use the Or keyword on the second one.

Quick - The condition is checked during all phases and all player's turns by default.

STActivation - Used for Spells and Traps. If this condition is not met, the Spell/Trap card cannot be activated in the first place (meaning, placed on the field face-up)

Resolve - This condition is checked twice : once when activating the effect, and once when resolving. If the condition is not met upon resolution, the action will fail (for example, Zombie Master must be face-up on the field to resolve its effect)

Looping - Normally for Trigger conditions underneath other effects, after the condition is checked, it is not revisited, unless the above effects are too. This keyword ensures that the condition will be checked over and over again without relying on the above effects.