PHB24 has re-implemented the Fighting Style mechanic from 2014 as a collection of Feats, rather than class-specific features.
The Fighter, Paladin, and Ranger classes gain the Fighting Style Feature at level 2, which is a prerequisite for a character to take any Feats in the Fighting Style category. Operationally, this ends up with the same result as PHB14: only certain classes get a Fighting Style. The functional difference now is that all of the Fighting Styles are available to a class that gets one, not just a hand-picked selection.
For example, under this new handling a Ranger could now take the Protection style - or a Paladin the Archery style - whereas the older rules limited the options to a class-specific set of options.
There is an organizational nicety in this change: the Fighting Styles are now all defined together on pages 209-210. Previously they were listed with their benefits in each of the class descriptions, which was useful for reviewing character-specific options, but involved a lot of page-flipping to compare all available styles across classes.
Archery - No change: +2 to Ranged attacks.
Blind Fighting - Imported from Tasha’s Cauldron of Everything. No change: ten feet of Blindsight.
Defense - No change: +1 to AC while wearing armor.
Dueling - No change: +2 to damage with one-handed melee weapons.
Great Weapon Fighting - PHB14 allowed re-rolling damage dice showing a 1 or 2 when using two-handed weapons. In PHB24 the re-roll is replaced with “the damage is 3”, all other conditions remain.
Interception - Imported from Tasha’s Cauldron of Everything. No change: reduces damage by 1d10 + Proficiency Bonus for a creature attacked within 5’, uses Reaction.
Protection - The triggering conditions and imposition of Disadvantage remain from 2014, but now applies Disadvantage to all subsequent attacks in the round as long as the Protector remains within 5’. Previously this only applied Disadvantage to the triggering attack.
Thrown Weapon Fighting - Imported from Tasha’s Cauldron of Everything. No longer specifies the ability to draw a Thrown weapon a part of an attack with it. Otherwise no change: +2 to damage with Thrown weapons.
Two-Weapon Fighting - No change: add ability modifier to two-weapon attack damage. The wording in PHB24 fully defines the requirements for two-weapon attacks, where '14 did not.
Unarmed Fighting - Imported from Tasha’s Cauldron of Everything. No change: upgrades Unarmed Strikes to 1d6 + Strength, further increases this to 1d8 if not holding weapons or shield, adds 1d4 per turn to a Grappled target without using any action economy.