The NY Times has a good summary: https://www.nytimes.com/2023/06/20/business/media/reddit-moderators-api-protest.html
Highlights:
65% of the 9,000 subs (message boards) went "dark" for 2 days, in protest
Protest is over Reddit charging large-scale companies for access
** like Google, OpenAI (ChatGPT), Microsoft...which uses Reddit content to train its AI models
** The protest concern is more about how it could kill off 3rd party apps, such as Apollo that is used on iOS to be a user-friendly Reddit interface (would cost Apollo $20 million annually), and how it would hurt tools that moderators use to manage freewheeling discussions on their sub