Source Player Core pg. 206
You are skilled at avoiding detection, allowing you to slip past foes, hide, or conceal an item.
Even if you’re untrained in Stealth, you can use it for the following general skill actions.
Conceal an Object- You hide a small object on your person
Hide- You huddle behind cover or greater cover or deeper into concealment to become hidden, rather than observed.
Sneak- You attempt to move to another place while becoming or staying undetected.
If you want to sneak around when there are creatures that can see you, use a combination of Hide and Sneak.
First, Hide behind something (either by taking advantage of cover or having the concealed condition due to fog, a spell, or a similar effect). A successful Stealth check makes you hidden, though the creatures still know roughly where you are.
Second, now that you're hidden, you can Sneak. That means you can move at half your Speed and
attempt another Stealth check. If it's successful, you're now undetected. That means the creatures don't know which square you're in anymore.
If you were approaching creatures that didn't know you were there, you could Sneak right away, since they didn't know your location to start with. Some actions can cause you to become observed again, but they're mostly what you'd expect, such as standing out in the open, attacking someone, or making a bunch of noise. Unobtrusive actions, such as Recalling Knowledge or reloading, allow you to remain hidden or undetected. If you Strike someone after successfully Hiding or Sneaking, though, they're off-guard to that Strike.
Creatures can try to find you using the Seek action.
Three conditions explain the states of detection. Remember that these conditions are relative to each creature—you can be observed by one creature while hidden to another and undetected by a third.
Observed You're in the creature's clear view.
Hidden The creature knows your location but can't see you.
Undetected The creature doesn't know your location.
In some cases, it can be impossible for a creature to fully observe you. Typically this happens if you're invisible, the observer is blinded, or you're in darkness and the creature can't see in darkness. In such cases, any critical failure you roll on a check to Sneak is a failure instead. You also continue to be undetected if you lose cover or greater cover against or are no longer concealed from such a creature.