illusions

Illusions can create images of objects, creatures, or other visible phenomena.
Until investigated, illusions seem completely real, possibly including sounds, smells, and temperature appropriate to the thing depicted. However, illusions can’t create sufficient heat or cold to cause Damage, a sound loud enough to deal Thunder Damage or Deafen a creature, or a smell that might sicken a creature. They can't create real, usable light or mimic the effects of sunlight, although you can create light using other means and then use that light in the illusion.
If two separate illusions interact, they behave as would seem natural if the illusion were real, unless the interaction is beyond the limits of whatever effect created the illusion.
Physical interaction with an illusion reveals its illusory nature, because things can pass through it. A creature that uses the search action to examine the image can determine that it is an illusion with a successful Intelligence (Investigation) check against a DC set by the GM, often the spell save DC of the creature that created the illusion. If a creature discerns the illusion for what it is, the creature can see through the image, and its other sensory qualities become faint to the creature.