Files you upload to or create in ChatGPT are now saved to your Library, so you can find and reuse them later. Library is currently available on web only.
ChatGPT automatically saves uploaded and created files, including files added in chats, for example documents, spreadsheets, presentations, and images, in a dedicated and secure location so they can be accessed later. Generated images will continue to appear in the Images tab.
Library is currently available only to ChatGPT Plus, Pro, and Business users outside the European Economic Area, Switzerland, and the United Kingdom.
https://help.openai.com/en/articles/20001052-file-storage-and-library-in-chatgpt