On most Android phones, open the file manager, enable the option to show hidden files, then navigate to Internal storage > ...

You'll see categories like apps, photos, videos, audio, cached data, and system files. Tap each one to see specific files consuming space and decide whether to delete them.

Wiping the Digital Camera Images folder is a lot like clearing out WhatsApp's hidden status stash. Both folders hold files you don't actively see. In this case, thumbnails and trashed.