A creature you're hidden from knows your location but can't see you.
Kind
Condition
Group
Detection
While you're hidden from a creature, that creature knows the space you're in but can't tell precisely where you are. You typically become hidden by using Stealth to Hide. When Seeking a creature using only imprecise senses, it remains hidden, rather than observed. A creature you're hidden from is off-guard to you, and it must succeed at a DC 11 flat check when targeting you with an attack, spell, or other effect or it fails to affect you. Area effects aren't subject to this flat check.
A creature might be able to use the Seek action to try to observe you, as described on page 417.
Detection conditions
Player Core groups Hidden with Observed, Undetected, Unnoticed.
Source: Pathfinder Player Core, p. 444
Bring Hidden into a Pathfinder 2e game with The DM Screen.