Abbreviations : In the following I am referring to Dungeons and Dragons as D&D , the Players Handbook as the PHB , the 2014 version as 5E and to the 2024 version as 5.5.

I am assuming that the reader is familiar with the 5E PHB, so I am only commenting on things that are new or different from the 5E version.

The descriptions below have been abbreviated. They are intended to serve as a guide to the changes. Please don’t consider these to be the rules, refer to the text in the book.

Hit Point Die: d8 per Monk Level
Saving Throw Proficiencies: Strength and Dexterity
Skill Proficiencies: Choose 2 from Acrobatics, Athletics, History, Insight, Religion, or Stealth
Weapon Proficiencies: Monk weapons (which are Simple weapons and Martial weapons that have the Light property).
Tool Proficiencies: Choose one type of Artisan’s Tools or Musical Instrument.
Armor Training: None
Choose A or B:
(A): Spear, 5 Daggers, Artisan’s Tools or Musical Instrument, Explorer’s Pack, and 11 GP
(B): 50 GP

Level 1, Martial Arts : (This has changed a bit.) You can use Dexterity instead of Strength for the attack and damage rolls of your unarmed strikes and monk weapons.

Level 1, Unarmored Defense : No change
Level 2, Dedicated Weapon : (This is new.) You can use your Monk’s Focus in place of the Ammunition property for one weapon that you are proficient with and are wielding. You must choose the weapon when you gain this feature. You can change this choice on a long rest.
Level 2, Monk’s Focus : (Ki Points are now called Focus Points) This is the same as the 5E rules, but it has added the option to use 1 Focus Point to take both the Disengage and the Dodge actions as a Bonus Action with Patient Defense, and to use 1 Focus Point to take both the Disengage and Dash actions as a Bonus Action with Step of the Wind.
Level 2, Unarmored Movement : No change
Level 2, Uncanny Metabolism : (This is new.) Once per long rest, when you roll Initiative you regain all Focus Points and regain hit points = Monk level + a roll of your Martial Arts die.
Level 3, Subclass : Described later. (Called Monastic Tradition in 5E)
Level 3, Deflect Attacks : (Replaces 5E’s Deflect Missiles) As a reaction, when hit and receive Bludgeoning, Piercing, or Slashing damage, the damage is reduced by 1d10+DEX mod. + Monk level. If that reduces the damage to 0, select another creature to receive damage of that type, spend 1 Focus Point, the creature must make a DEX save or take damage = your DEX mod + 2 rolls of your Martial Arts die. The creature you select must be within 5 feet if you were hit with a melee attack, or 60 feet if it was a ranged attack.
Level 4, Ability Score Improvement : “You gain the Ability Score Improvement feat (see chapter 5) or another feat of your choice for which you qualify. You gain this feature again at Monk levels 8, 12, and 16.” This is the same as it was in 5E, it just made the ability score improvement a feat, and lets you choose another feat instead if you want to. Another minor change is that you don’t get this at level 19 anymore, you will get an Epic Boon instead (see below).
Level 4, Slow Fall : No change
Level 5, Extra Attack : No change
Level 5, Stunning Strike : (This has changed a bit.) Once per turn when you hit a creature with a Monk weapon or an Unarmed Strike, if you spend a Focus Point, that creature must make a CON save or be stunned until the start of your next turn. If it fails the save it’s Speed is halved instead, and the next attack against it until then has Advantage.
Level 6, Ki-Empowered Strikes : (Replaces Ki-Empowered Strikes and is different.) You can cause your Unarmed Strikes to deal Force damage.
Level 7, Evasion : No change
Level 7, Stillness of Mind : No change
Level 9, Acrobatic Movement : (This is new.) When not wearing armor or shield, you can walk on vertical surfaces and liquids.
Level 10, Heightened Focus : (This is new.) Flurry of Blows, Patient Defense, and Step of the Wind gain the following benefits.

Level 10, Self-Restoration : (Replaces 5E’s Purity of Body.) Can remove Charmed, Frightened, or Poisoned condition from yourself at the end of your turn. Also, you don’t receive levels of Exhaustion when you have no food or drink.
Level 11, Perfect Focus : (This has changed.) If you are concentrating on a spell when you take damage, you can expend 1 Ki point to maintain your Concentration.
Level 13, Deflect Energy : (Replaces 5E’s Tongue of the Sun and Moon.) Your Deflect Attacks feature now works against all types of damage.
Level 14, Disciplined Survivor : No change (RE-named 5E’s Diamond Soul.)
Level 15, Perfect Focus : (Replaces 5E’s Timeless Body.) “When you roll Initiative and don’t use Uncanny Metabolism, you regain expended Focus Points until you have 4 if you have 5 or fewer.”
Level 18, Superior Defense : (Replaces 5E’s Empty Body.) Spend 5 Focus Points to get Resistance to all except Force damage for 1 minute.
Level 19, Epic Boon : All classes get an epic boon feat at 19th level. There is a separate list of feats that are in the Epic Boon Category.
Level 20, Body and Mind : (Replaces 5E’s Perfect Self.) Your DEX and WIS scores increase by 4, to a maximum of 25.

The D&D 5E PHB has 3 subclasses, the PHB 5.5 has 4; the Warrior of Mercy, the Warrior of Shadow (Way of Shadow in 5E), the Warrior of the Elements (Way of the Four Elements in 5E), and the Warrior of the Open Hand (Way of the Open Hand in 5E).

Warrior of Mercy (This is a new subclass.)

Level 3, Hand of Harm : Spend 1 Focus Point to add Necrotic damage to an unarmed strike = 1 Martial Arts die roll + your WIS mod.
Level 3, Hand of Healing : Can replace 1 unarmed strike in a Flurry of Blows, or Spend 1 Focus Point, to heal HP = 1 Martial Arts die roll + WIS mod.
Level 3, Implements of Mercy : “You gain proficiency in the Insight and Medicine skills and proficiency with the Herbalism Kit.”
Level 6, Physician’s Touch : Hand of Harm and Hand of Healing improve.

Level 11, Flurry of Healing and Harm : Flurry of Blows can replace each of the Unarmed Strikes with a use of Hand of Healing without using Focus Points for the healing. Also, when you make an Unarmed Strike with Flurry of Blows and deal damage, you can use Hand of Harm with that strike without spending a Focus Point for Hand of Harm.
Level 17, Hand of Ultimate Mercy : Once per long rest, you can spend 5 Focus Points to return a creature to life, that died within the past 24 hours, with HP = 4d10 + your WIS mod. and any Blinded, Deafened, Paralyzed, Poisoned, or Stunned condition it died with are removed.

Warrior of Shadow (Way of Shadow in 5E)

Level 3, Shadow Arts : (Minor changes)
You can spend 1 Focus Point (2 ki points in 5E) to cast these spells:

Level 6, Shadow Step : No change.
Level 11, Improved Shadow Step : (Cloak of Shadows in 5E, you could become invisible) When you use your Shadow Step, you can spend 1 Focus Point to not have to start and end in Dim Light and you can make an Unarmed Strike immediately after you teleport.
Level 17, Cloak of Shadows Opportunist’s Strike : (Replaces 5E’s Opportunist.) Spend 3 Focus Points when in Dim Light or Darkness to shroud yourself with shadows for 1 minute unless you end your turn in Bright Light. Also; you are Invisible, can move through occupied spaces as Difficult Terrain, and can use your Flurry of Blows without spending any Focus Points.

The biggest difference is that in 5E you can cast Elemental Spells. That ability has been removed and all of the features have been changed as indicated here.

Level 3, Elemental Attunement : Spend 1 Focus Point to gain the following benefits for 10 minutes.

Level 3, Manipulate Elements : You know the Elementalism spell. (This is a new spell for 5.5)
Level 6, Elemental Burst : Spend 2 Focus Points to cause creatures in a 20-foot-radius Sphere within 120 feet of you to make a DEX save or take Acid, Cold, Fire, Lightning, or Thunder damage = 3 rolls of your Martial Arts die, half on a save.
Level 11, Stride of the Elements : “While your Elemental Attunement is active, you also have a Fly Speed and a Swim Speed equal to your Speed.”
Level 17, Elemental Epitome : While your Elemental Attunement is active, you also get:

Level 3, Open Hand Technique : (Minor change)
The target not being able to take Reactions in 5E was changed in 5.5 to can’t make Opportunity Attacks.
Level 6, Wholeness of Body : (Changed somewhat.)
As a Bonus Action, you heal yourself, HP = 1 roll of your Martial Arts die + your WIS mod. You can do this a number of times equal to your WIS mod. You regain all expended uses on a Long Rest.
Level 11, Fleet Step : (Replaces 5E’s Tranquility.) “When you take a Bonus Action other than Step of the Wind, you can also use Step of the Wind immediately after that Bonus Action.”
Level 17, Quivering Palm : (Changed a little) The only differences are these.