Short Rest

A short rest is a period of downtime, at least 1 hour long, during which you do nothing more strenuous than eating, drinking, reading and tending to wounds.
At the end of a short rest:

• Spend one or more hit dice to heal. For each hit die spent, roll the die and add your Constitution modifier to see how many hit points you recover.
• A bard can use Song of Rest during a Short Rest to give everyone who spent hit dice during that rest an extra 1d6 hit points (roll once for all characters)
• Higher-level bard regains inspiration dice
• Warlocks regain spell slots and Fey Presence and Misty Escape abilities
• Once per day, Wizards can regain spell slots equal to half (rounded up) their wizard level
• Characters can receive the benefit of an Inspiring Speech
• Druid regains wildshape

Long Rest / Sleep

• Synonymous with a good night’s sleep

A long rest is a period of extended downtime, at least 8 hours long, during which you sleep or spend no more than 2 hours performing light activity: reading, talking, eating, or standing watch. If the rest is interrupted by a period of strenuous activity—at least 1 hour of walking, fighting, or similar adventuring activity—you must begin the rest again to gain any benefit.
At the end of a long rest, you regain all lost hit points. You also regain hit dice equal to half your character level (rounded down).

Elves gain the full benefits of a long rest by meditating for 4 hours.

• You can’t benefit from more than one long rest in a 24-hour period
• You can’t begin a long rest until you have been awake for at least 16 hours
• You have to have at least 1 hit point at the start of the rest to gain its benefits.

Other Long Rest Recovery:

• All powers regained from a short rest
• All spell slots
• Clerics, Druids and Wizards regain the ability to clear their prepared spell lists
• Grave Cleric Eyes of the Grave ability
• Temporary hit points go away
• Magic items regain some of their charges
• Conjurer Benigh Transposition

Long Rest and Adverse Conditions

Uncomfortable or stressful circumstances make it difficult to benefit from a long rest. An ability check might be required to get any benefit from a long rest in the following situations:

• Extreme Weather (heavy rain or snow without shelter): DC20 CON save
• Sleeping in Armor: Light (DC10), Medium or shield (DC15), Heavy (DC20) CON save
• Extreme Stress (sounds of torment, undead haunting, in Leomund’s Tiny Hut with hostiles directly outside): DC15 WIS save

foregoing sleep

• After 24 hours finishing a long rest → DC10 CON save or +1 exhaustion
• DC increases by 5 for each 24 hours without sleep