when I am deleting data on my iPhone a message pops up saying if you delete this it will be deleted across all devices what does that mean

soverocker wrote:

up saying if you delete this it will be deleted across all devices what does that mean

It appears to me that you are attempting to delete a Messages thread, and the advisory means that the thread you selected will be "deleted from all of your devices" if you choose "Delete."

This means that this data is stored in iCloud and is synched to all devices. If you delete from one device, it will be deleted on all devices that are connected to that iCloud account. For that reason I never store anything important in iCloud. It is too easy to accidentally delete from one device and lose it on all devices.