From the PHB, Appendix A on Conditions:
INVISIBLE
- An invisible creature is impossible to see without the aid of magic or a special sense. For the purpose of hiding, the creature is heavily obscured. The creature's location can be detected by any noise it makes or any tracks it leaves.
- Attack rolls against the creature have disadvantage, and the creature's attack rolls have advantage.
One of my players was sneaking around while invisible. Unfortunately, his Stealth roll failed to beat an NPC's Passive Perception, so he was detected. What does 'detected' actually mean?
I ruled at the time that the NPC could tell someone was there but not exactly where (because she heard the noise made by someone moving), but RAW, did she know exactly where he was?
Best Answer
Ok, crazy thing about the difference between hidden and invisible...there isn't much of one.
The big difference between the two is the ability to be attacked directly. If you are hidden, your enemy doesn't know your location, and thus cannot target you directly. They have to guess (DM should use some kind of randomization here), and may or may not actually be targeting you (See "Unseen attackers and targets" p194 of PHB).
In contrast if you are only invisible, then your enemy knows where you are and can attack you directly at disadvantage. The biggest benefit of Invisible is that it provides you with the conditions to hide continuously instead of having to find cover all the time.
The other thing this is important for is that an invisible, but detected creature isn't going to get a surprise round. An invisible but hidden creature will.