You may have gotten emails from Apple, or seen articles, about Apple’s My Photo Stream ending service on July 26th.
My Photo Stream was a service launched in 2011 that temporarily uploaded photos from one device so you could see them on other devices.
Most people probably are not using My Photo Stream any more, as iCloud Photos is a better way to sync photos across devices.
To check if you are using My Photo Stream on iPhone and iPad: Go to Settings > (your name) > iCloud > Photos, and if “Sync This iPhone/iPad” is enabled, and you see no mention of My Photo Stream, you’re fine.
To check on Mac: Open the Photos app and then from the Photos menu choose Preferences > iCloud. If “iCloud Photos” is enabled, and there’s no mention of My Photo Stream, you’re fine.
If you are using My Photo Stream, you’ll need to make some changes or your photos may be deleted. Basically you want to save the photos and then turn on iCloud Photos.
Here’s more info and instructions at Apple: Information about the My Photo Stream shutdown