Imagine you’re sitting down, on the interweb, doing you own thing. Not too far away is someone playing the same game that you are. It is a storyline you haven’t finished yet but are currently actively playing. Said person starts talking. Now up until this point, you’ve avoided spoilers as much as possible. Looking the other way during scenes and the likes. However this person starts talking about a later mission, giving away vital details. You’ve just been spoiled and this is Gamer Etiquette.