Hello Danee2006,
It sounds like photos and videos were downloaded to your Mac from iCloud, and you want to know how to remove them, correct? We'd love to provide some information.
Just to confirm, do you recall if you selected the option to download originals when you turned on Optimize Storage?
"If you have Optimize Storage turned on, you might not have all of your original photos and videos on your device. To download the original photos and videos on your iOS device, go to Settings > [your name] > iCloud > Photos and select Download and Keep Originals. On your Mac, open Photos, choose Photos > Preferences, then select Download Originals to this Mac. Then you can turn off iCloud Photos. You can also select the photos and videos that you want to download from iCloud.com.
Before you turn off iCloud Photos, you might want to make a copy of your photos and videos." You can find more information about how to manage iCloud Photos here: Get help with iCloud Photos
If you want to delete photos from iCloud on your Mac, please check out this page: Delete photos from iCloud using Photos on Mac
Take care!