Metagaming

Knowledge the players have that their characters don't is often called “metagame knowledge,” and using it to influence characters' decisions is called “metagaming.” Some metagaming results naturally from play and is wise to disregard. The witchwarper aiming corrosive haze precisely enough to include three enemies in the very edge of the spell's area is probably unrealistic, but isn't that disruptive to play. Things get more questionable if the player says something like “That's a cybernetic zombie, so don't get too close because they self-destruct” regardless of whether their character has encountered a cybernetic zombie before or identified the creature. Each group is different, and the assumption of what the characters know varies. If metagaming starts to get out of hand, you might use some gentle reminders, like “I'm not sure your character's aware of that” or “Can you explain your character's thinking when they do that?” If the problem persists, see the guidelines mentioned in the Problematic Players section.