This isn't really accurate.

So, a brief history: Once Upon A Time there was TSR, which published two lines of D&D books, based on the original D&D: Dungeons and Dragons (which started with the Basic Set and added other sets over time) and Advanced Dungeons and Dragons, which got two editions. TSR went bankrupt and was bought by Wizards Of The Coast, which was flush with cash from the success of Magic: The Gathering. They put out a Third Edition for D&D, which unified both lines but kept the AD&D numbering, hence Third Edition. It was a rather thorough reworking of the rules to D&D -- everthing is unified around a central mechanic using d20 (20-sided dice, which is why the underlying rules are called the "d20 System"), which eliminates a bunch of tables and complexity. The game removed restrictions around what races could use what classes and got rid of a lot of the vestiges of old D&D, where "elf" was a character class in the same way that "thief" was. It introduced feats... essentially, D&D 3rd Edition was a new game compared to AD&D 2nd Edition. They bundled up a bunch of errata into what was awkardly called the "3.5th Edition" at some point down the line, and most books published for 3rd Edition were really 3.5th Edition books.

At the time, Wizards of the Coast did two things that are notable here:

1) They licensed a third-party company, Paizo, to publish the Dungeon and Dragon magazines. Paizo did a brisk business in these, driven in part by their popular "adventure paths."
2) They released a stripped down version of the core rulebooks, removing some "product identity" and some of the rules around character creation, as the System Reference Document, which was released under the Open Gaming License, basically an open source license for RPG materials. The point of the OGL/SRD was to allow people to publish third-party supplements for D&D. This _mostly_ went very well, but there were some releases that WotC was unhappy with, either because they were controversial (like the Book of Erotic Fantasy) or because they were not supplements for D&D but competing games using the d20 System that Wizards had built for D&D.

At the end of 3rd Edition, they announced a Fourth Edition, which was roughly as radical a departure from 3rd Edition as 3rd Edition was from AD&D 2nd Edition. They also revoked Paizo's license to publish material for D&D, and they decided that 4th Edition wouldn't be released under the OGL, and they released a much less useful "System Reference Document" under a much more restrictive license. Paizo's entire business at the time was D&D 3.5th Edition supplements, so this left them out in the cold. So what they did was release a new game, Pathfinder, based on the 3.5th Edition SRD, published under the OGL. The changes from 3.5th Edition to Pathfinder First Edition were pretty small, which led it to be nicknamed "3.75th Edition" by D&D players around the time of its release.

And, despite WoTC owning the rights to all of the trademarks -- all of the popular settings, NPCs, what have you -- Pathfinder outsold D&D 4th Edition. Because it was a lot more comfortable with what 3rd Edition players wanted from the game.

D&D 5th Edition basically throws out most of the changes from 4th Edition and goes back to a 3rd Edition base. It is streamlined from 3rd Edition, but if you have played 3rd Edition or Pathfinder and you want to play a 5th Edition game someone can teach you enough to start playing in about seven minutes.

The tradeoff is that 5th Edition has far fewer options to customize characters than 3rd Edition did, but is more streamlined and easier to adjudicate at the table. Pathfinder has retained much more of the spirit of 3rd Edition in the sense of giving a lot of options to customize characters. But neither of them is, in a rules sense, closer to AD&D than the other.