Clearly the answer is all of the above, but the lines are blurred enough to confuse customer expectations and sometimes the designers themselves
For example, if a card deals 3 damage to an opponent, its controller gains 3 life
Youre likely going to be printing these business cards out, so dont use a color that will use up a lot of ink unless you have an industrial size printer (or a lot of ink going spare)
You won't gain 1 life for a creature that isn't actually destroyed, such as a creature with indestructible
Triggered abilities use the word "when," "whenever," or "at." They're often written as "[Trigger condition], [effect]." Replacement effects, using "instead" or "as," aren't affected
Nogi, Draco-Zealot not only cuts dragon costs, but it eventually turns into a 5/5 flying threat once your board is built up