Hide

When you take the Hide action, you attempt to reduce your visibility and keep as quiet as possible in order to escape detection. 
If you succeed, you gain certain benefits, as described in "Unseen Attackers and Targets".

Hiding Rules

The DM decides when circumstances are appropriate for hiding. When you try to hide, simply declare it. 
At the next moment of possible detection by an enemy, make a Dexterity (Stealth) Skill Check. This is an Opposed Check; the DC for the check is a passive Perception Skill Check -- 8 + the Wisdom modifier of the enemy with the highest Perception score. Opponents proficient in Perception can add their Proficiency Bonus. If the enemy creature has Advantage or Disadvantage on the skill, apply +5 or -5 to the DC. Any bonus that can be granted to the target’s perception skill, such as from a priest’s Bless spell may also be applied to the DC.
If enemies are actively searching for hidden creatures, the check becomes an active Dexterity (Stealth) Skill Check Contested by the Wisdom (Perception) check of the creature with the highest Perception proficiency score.
You can't hide from a creature that can see you clearly, and you give away your position if you make noise, such as shouting a warning or knocking over a vase. An Invisible creature can always try to hide. Signs of its passage might still be noticed, and it does have 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 GM might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain Advantage on an Attack roll before you are seen.
Passive Perception. When you hide, there's a chance someone will notice you even if they aren't searching -- treat this as an Opposed Check. To determine whether such a creature notices you, the GM compares your Dexterity (Stealth) Skill Check with that creature's passive Wisdom (Perception) score, which equals 8 + the creature's Wisdom modifier, as well as any other bonuses or penalties. If the 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 12.
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 Obscured or Heavily obscured.