Photos

Are you using iCloud Photos to sync your Mac and your iPhone? If so, then yes. Any photo deleted from any of the devices connected to your iCloud Photo Library will be deleted from the cloud, then deleted from the other device(s) connected to that library.

If you had manually copied photos from your iPhone to your Mac, then they would retain no connection. However, a future manual copy might copy them again.

If you used some other mechanism to copy photos between your Mac an your iPhone, please tell us how you did it.

Another point to consider: You may want to be sure to make a current backup of your devices, before you start with a massive deletion.

It is easy to delete accidentally the wrong photos. If you are using iCloud Photos you should be aware, that the iCloud backup of your iPhone does not include the photos (only a backup on a computer will include the photos, if iCloud Photos is enabled). And if "Optimize Storage" should be enabled, no backup will include the optimised version, because they originals are only in iCloud. Then you have to backup your photos by exporting them from Photos to a backup volume.