Later this week Paizo will be releasing the first books of Pathfinder Remastered.
Nothing is being taken out (you can still use all the content from older books), but a fair bit of content is getting errata'd, mostly for the better.
The new books are called Player Core and GM Core and they include content from The older Core Rulebook and Advanced Player's Guide. In the future, Paizo will also be releasing Monster Core and Player Core 2.
One reason why you might have been told that things were "being taken out" is that the classes and several options have been split up between Player Core 1 and Player Core 2. You will still be able to use content from Secrets of Magic, Guns and Gears, Dark Archives, and other amazing books. These and other PF2e books will not be rereleased under the Remaster (since they will largely work "as is"), though they may see some limited online errata that you may want to look out for (which can be found here).
The former has the Bard, Cleric, Druid, Fighter, Ranger, Witch, and Wizard; whereas the latter will have the Alchemist, Barbarian, Champion, Investigator, Monk, Oracle, Sorcerer, and Swashbuckler.
That creates this weird middle ground, where some classes benefit from awesome new updates, while others will be forced to use the older pre-errata rules for several months before they catch up with their own awesome updates.
Another reason you might have heard that is because Alignment is being removed from the game. Wizard schools are also undergoing significant changes (to the point where some people might say they are effectively being taken out).
None of that matters if your play group doesn't intend to use the Remaster content, however, and none of the Remaster content replaces anything other than what's in the Core Rulebook, the GameMastery Guide, the Advanced Player's Guide, and the Bestiary. Your copy of the Core Rulebook is not obsolete unless your group decides for it to be.
If you want to take advantage of the changes coming in the Remaster, then you would need to pay for as many as four new books.
It may also be worth noting that Paizo is not doing this necessarily because they wanted to (it's not a money grab or a new edition), but because they were forced to by their chief competitor, Wizards of the Coast (owned by Hasbro) who threatened to sue them. As such, much of the Remaster content is little more than name changes to various feats, spells, and other abilities that are intended to reduce the likelihood of Paizo seeing litigation (even though Paizo is in the right, they can't afford to take on a financial power house that is Hasbro). Paizo wanted to turn a bad situation into a positive one though, and so they're using it as an opportunity to implement a lot of errata to make the game better.
I hope that helps. If you need more information, I'll be here to answer any additional questions you might have. Also, you can check out Paizo's official announcements regarding the Remaster in their Blog here. There is also tons of information and commentary on Reddit and YouTube covering the Remaster.