When I need to upload a photo to a site the folders page pops up(home,desktop,video etc.) but the files aren't there to upload.Why don't I have access to them with the browser?

I can't upload files such as photos to AI generators.When I try to upload the list of folders pop up but when I click on any of the folder the content I know is there doesn't appear. Why? At the bottom of this question area there is an image upload option but for some reason I am unable to access my files to upload. I am perplexed.