A Microsoft file hosting and synchronization service.
I think it's fixed now. MS suggested, open Onedrive on your browser(If this is where your problem is). Choose Settings at top right, Then choose Options, then choose Photos from the left side. then select Hide for now. Mine is now gone!
There's a work around also. Right click on each item showing at the top(Videos or pictures). On Brave browser, I then choose Brave, and from the pop up menu I choose Block element. It will then just be a blank rectangle.
I went back and forth with MS. They suggested several things, which did not work. Finally they come up with a real fix. Hope this helps.