The “System Data” or “Other” category in your iPhone’s storage includes caches, settings, messages, voice memos, and miscellaneous data. The good news is that you can clear out much of this unused data to reclaim valuable space on your iPhone.
Occasionally you’ll find strange images in your gallery that, for the life of you, you don’t remember downloading. Then you get an inkling to check your WhatsApp chats, and it hits you—WhatsApp automatically downloaded them from your chats and groups.