Activated abilities are written in the form “Cost: Effect.” Some keyword abilities, such as equip and crew, are activated abilities and will have colons in their reminder texts.

Triggered abilities use the word “when,” “whenever,” or “at.” They’re often written as “[Trigger condition], [effect].” Some keyword abilities, such as prowess and fabricate, are triggered abilities and will have “when,” “whenever,” or “at” in their reminder text.

If you counter a delayed triggered ability that triggers at the beginning of the “next” occurrence of a specified step or phase, that ability won’t trigger again the following time that phase or step occurs.

Abilities that create replacement effects, such as a permanent entering the battlefield tapped or with counters on it, can’t be targeted. Abilities that apply “as [this creature] enters the battlefield” are also replacement effects and can’t be targeted. Similarly, the replacement effect that prevents a creature with a stun counter on it from untapping can’t be countered.