The Files section contains all files which are attached to the sheet. There could be files which are not in the sheet.
You can use Files to upload multiple files at once.
You have to choose between a few methods to upload:
- Local - upload files from your computer
- Google Drive - upload files from your Google Drive account
- Dropbox - upload files from your Dropbox account
- OneDrive - upload files from your OneDrive account
When you are done with the uploading you can use the files in the Sheet.