Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keyword abilities, like equip, are activated abilities and they have colons in their reminder text.

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

Players can respond to the triggered ability that exiles nontoken creatures that die. If the card leaves the graveyard before the ability resolves, Koh will not exile the card and it cannot be chosen with Koh's activated ability.