https://www.xbox.com/en-US/xbox-game-pass/core

Microsoft is ending Xbox Live Gold, and it will be replaced with a new tier of Game Pass called “Core”, starting September 14, 2023.

Most things will remain the same (such as the price), but there are a couple of notable changes:

The “Games With Gold” program will not be continued (1) Instead, members will gain access to 25 games from the Game Pass library, as selected by Microsoft (with supposedly a few being added every year) Subscribers of Xbox Live Gold will be automatically moved over to Game Pass Core when it starts on September 14th.

(1) In regards to members with previous GwG items in their libraries, any claimed Xbox One titles will remain in their library as long as they continue their Game Pass Core subscription, and any claimed Xbox 360 games will be available regardless of subscription status - just like how Games with Gold worked previously