Conditions
Blinded
You can't see and automatically fail any ability check that needs sight. Attack rolls against you have Advantage, and your attack rolls have Disadvantage.
Charmed
You can't attack the creature that charmed you or target it with damaging abilities or magical effects. The charmer has Advantage on ability checks to interact with you socially.
Deafened
You can't hear and automatically fail any ability check that needs hearing.
Exhaustion
Exhaustion is cumulative: each time you get it you gain a level. Every D20 Test you make is reduced by 2 times your Exhaustion level, and your Speed is reduced by 5 feet times your level. You die at level 6. A Long Rest removes one level; at level 0 the condition ends.
Frightened
While the source of your fear is within line of sight, you have Disadvantage on ability checks and attack rolls. You can't willingly move closer to the source of your fear.
Grappled
Your Speed is 0 and can't increase. You have Disadvantage on attack rolls against any target other than the grappler. The grappler can drag or carry you, paying 1 extra foot per foot moved unless you are Tiny or two or more sizes smaller than it.
Incapacitated
You can't take any action, Bonus Action or Reaction, and you can't speak. Your Concentration is broken. If you are Incapacitated when you roll Initiative, you have Disadvantage on the roll.
Invisible
If you are Invisible when you roll Initiative, you have Advantage on the roll. Effects that need to see their target don't affect you unless their creator can see you, and neither does anything that targets your gear. Attack rolls against you have Disadvantage and your attack rolls have Advantage, except against a creature that can somehow see you.
Paralyzed
You have the Incapacitated condition and your Speed is 0 and can't increase. You automatically fail Strength and Dexterity saving throws. Attack rolls against you have Advantage, and any attack that hits you is a Critical Hit if the attacker is within 5 feet of you.
Petrified
You and the nonmagical things you wear and carry turn into an inanimate substance, usually stone; your weight is multiplied by ten and you stop aging. You have the Incapacitated condition, your Speed is 0 and can't increase, attack rolls against you have Advantage, and you automatically fail Strength and Dexterity saving throws. You have Resistance to all damage and Immunity to the Poisoned condition.
Poisoned
You have Disadvantage on attack rolls and ability checks.
Prone
Your only movement options are crawling or spending half your Speed (rounded down) to stand up, which ends the condition; with Speed 0 you can't stand. You have Disadvantage on attack rolls. An attack roll against you has Advantage if the attacker is within 5 feet of you, and Disadvantage otherwise.
Restrained
Your Speed is 0 and can't increase. Attack rolls against you have Advantage and your attack rolls have Disadvantage. You have Disadvantage on Dexterity saving throws.
Stunned
You have the Incapacitated condition. You automatically fail Strength and Dexterity saving throws, and attack rolls against you have Advantage.
Unconscious
You have the Incapacitated and Prone conditions and drop whatever you are holding; when this ends you are still Prone. Your Speed is 0 and can't increase. Attack rolls against you have Advantage, you automatically fail Strength and Dexterity saving throws, any attack that hits you from within 5 feet is a Critical Hit, and you are unaware of your surroundings.