In case it helps highlight anything, here's a copy paste of the PHB's segments on stealth and hiding curated as if it were its own article. The actual content itself should be minimally edited (i.e., it's directly copied except where it wouldn't make grammatical sense) but feedback is certainly welcome if something seems off.
STEALTH
HIDING When you try to hide, make a Dexterity (Stealth) check. Until you are discovered or you stop hiding, that check’s total is contested by the Wisdom (Perception) check of any creature that actively searches for signs of your presence.
You can’t hide from a creature that can see you, and if you make noise (such as shouting a warning or knocking over a vase), you give away your position. An invisible creature can’t be seen, so it can always try to hide. Signs of its passage might still be noticed, however, and it still has to stay quiet.
In combat, most creatures stay alert for signs of danger all around, so if you come out of hiding and approach a creature, it usually sees you. However, under certain circumstances, the Dungeon Master might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack before you are seen.
PASSIVE PERCEPTION When you hide, there’s a chance someone will notice you even if they aren't searching. To determine whether such a creature notices you, the DM compares your Dexterity (Stealth) check with that creature’s passive Wisdom (Perception) score, which equals 10 + the creature’s Wisdom modifier, as well as any other bonuses or penalties. Ifthe creature has advantage, add 5. For disadvantage, subtract 5. For example, if a 1st-level character (with a proficiency bonus of +2) has a Wisdom of 15 (a +2 modifier) and proficiency in Perception, he or she has a passive Wisdom (Perception) of 14.
What Can You See One of the main factors in determining whether you can find a hidden creature or object is how well you can see in an area, which might be lightly or heavily 10 as explained in chapter 8
HIDE
When you take the Hide action, you make a Dexterity (Stealth) check in an attempt to hide, following the rules in chapter 7 for hiding. lf you succeed, you gain certain benefits, as described in the "Unseen Attackers and Targets" section later in this chapter.
UNSEEN ATTACKERS AND TARGETS
Combatants often try to escape their foes' notice by hiding, casting the invisibility spell, ar lurking in darkness. When you attack a target that you can't see, you have disadvantage on the attack roll. This is true whether you're guessing the target's location ar you're targeting a creature you can hear but not see. If the target isn't in the location you targeted, you automatically miss, but the DM typically just says that the attack missed, not whether you guessed the target's location correctly.
When a creature can't see you, you have advantage on attack rolls against it. lf you are hidden-both unseen and unheard-when you make an attack, you give away your location when the attack hits or misses.
VISION AND LIGHT
The most fundamental tasks of adventuring—noticing danger, finding hidden objects, hitting an enemy in combat, and targeting a spell, to name just a few— rely heavily on a character’s ability to see. Darkness and other effects that obscure vision can prove a significant hindrance.
A given area might be lightly or heavily obscured. In a lightly obscured area, such as dim light, patchy fog, or moderate foliage, creatures have disadvantage on Wisdom (Perception) checks that rely on sight. A heavily obscured area—such as darkness, opaque fog, or dense foliage—blocks vision entirely. A creature in a heavily obscured area effectively suffers from the BLINDED condition:
• A blinded creature can’t see and automatically fails any ability check that requires sight.
• Attack rolls against the creature have advantage, and the creature’s attack rolls have disadvantage.
The presence or absence of light in an environment creates three categories of illumination: bright light, dim light, and darkness. Bright light lets most creatures see normally. Even gloomy days provide bright light, as do torches, lanterns, fires, and other sources of illumination within a specific radius. Dim light, also called shadows, creates a lightly obscured area. An area of dim light is usually a boundary between a source of bright light, such as a torch, and surrounding darkness. The soft light of twilight and dawn also counts as dim light. A particularly brilliant full moon might bathe the land in dim light.
Darkness creates a heavily obscured area. Characters face darkness outdoors at night (even most moonlit nights), within the confines of an unlit dungeon or a subterranean vault, or in an area of magical darkness.
BLINDED
- A blinded creature can't see and automatically fails any ability check that requires sight.
- Attack rolls against the creature have advantage and the creature's attack rolls have disadvantage,
Yo! I wanted to clarify and correct some of the stealth and perception procedures in my campaigns. The hiding/stealth/perception sections are spread out and I found it helpful to organize them as if they were a single section.
HIDING
When you take the Hide action, you make a Dexterity (Stealth) check in an attempt to hide. lf you are hidden when you make an attack, you have advantage on attack rolls and give away your location when the attack hits or misses. Likewise, you have disadvantage attacking a target that is hidden from you. If a target isn't in the location you targeted, you automatically miss.
To hide, you must be heavily obscured and unheard. For example, an invisible creature is heavily obscured, so it can always try to hide. Signs of its passage might still be noticed, however, and it still has to stay quiet.
The DC of your Dexterity (Stealth) check is the Passive Perception score of those you’re hiding from. Creatures with advantage or disadvantage to perceive you gain +5 or -5 to their Passive Perception, respectively. If a creature searches for signs of your presence, your check is contested by that creature's Wisdom (Perception) check.
You are discovered if the result your Dexterity (Stealth) check is below the creature’s Passive Perception or Wisdom (Perception) check. You are also discovered if you’re no longer heavily obscured from a creature you’re hiding from, make noise, or choose to stop hiding (no action required).
In combat, most creatures stay alert for signs of danger all around, so if you come out of hiding and approach a creature, it usually sees you. However, under certain circumstances, the Dungeon Master might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack before you are seen.
You cannot hide from a creature that can see you, so success relies heavily on a character’s surrounding light levels and visual obstructions. You are uncovered or unobscured in bright light where most creatures see normally. Even gloomy days provide bright light, as do torches, lanterns, fires, and other sources of illumination within a specific radius.
Dim light, also called shadows, creates a lightly obscured area. In a lightly obscured area, such as dim light, patchy fog, or moderate foliage, creatures have disadvantage on Wisdom (Perception) checks that rely on sight. An area of dim light is usually a boundary between a source of bright light, such as a torch, and surrounding darkness. The soft light of twilight and dawn also counts as dim light. A particularly brilliant full moon might bathe the land in dim light. Certain features (such as the Wood Elf’s Mask of the Wild trait or the Skulker feat) enable you to hide while only lightly obscured, otherwise, you can only hide while heavily obscured.
Darkness creates a heavily obscured area. Characters face darkness outdoors at night (even most moonlit nights), within the confines of an unlit dungeon or a subterranean vault, or in an area of magical darkness. Any natural phenomena that blocks vision entirely (such as opaque fog, or dense foliage) also heavily obscure you. A heavily obscured area doesn’t blind you, but you are effectively blinded when you try to see something obscured by it.
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This section below isn't taken from the PHB but is part of the document I have on my end for the purposes of quick reference for the table.
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Two heavily obscured combatants roll normally. The advantage granted by attacking a blind target is cancelled out by the disadvantage of being a blind attacker.
The roll for a heavily obscured combatant attacking a less obscured target rolls depends on the attacker’s ability to see through the obscurity. If the attacker can’t see through the obscurity (as would be the case with dense foliage or the effects of the Fog Cloud spell) the combatants roll normally as they are effectively blind to each other.
Alternatively a heavily obscured attacker who can see through the obscurity (for example, shooting out of darkness into an area of bright light) rolls with advantage since the target is effectively blind to the attacker but not vice versa.
Inversely, a less obscured combatant targeting a heavily obscured target rolls normally unless the target is able to see through the obstruction. If so, the attacker has disadvantage because there’s no mutual condition of blindness to cancel out (dis)advantage.
If you have multiple forms of obstruction, you’re concealed only by the most covering source of obstruction. For example, if you’re hiding in moderate foliage in dim light, you’re are lightly obscured. The two sources of obstruction do not create a sum of heavy obstruction.
