If you're working in Pages, Numbers, or Keynote and have created a file that's larger than 500 MB, saving it as a package helps the app you're using perform better. A package is a collection of files that your Mac reads as one file. By default, Pages, Numbers, or Keynote auto-saves a document, spreadsheet, or presentation as a single file.
If movies aren't playing correctly in Keynote, save your presentation as a package instead of as a single file.
If you experience performance issues with Pages, Numbers, or Keynote and you aren’t planning to send or store the document using a third-party cloud storage service, then save as package. Otherwise, it's best to save as a single file.
Save as a package or a single file
If your document is 500 MB or larger, you might be asked to save your document, spreadsheet, or presentation as a package. This can happen if you aren’t using Apple File System (APFS) or if you have an older version of Pages, Numbers, or Keynote.
Choose "Keep Single File" if you plan to send your document to a non-iCloud internet service such as iTunes U, Dropbox, Gmail, or another site where you upload files through your web browser.
Choose "Use Package" if you're saving your document to your hard drive, or if you're experiencing wait cursors or slow performance when editing your document.
You can switch between a single file and a package at any time. Open your file. Then choose File > Advanced > Change File Type, and select the type you'd like to use.
If your package is damaged and can't be opened
Documents saved as a package are sometimes damaged when they are uploaded to email or file sharing services in a web browser. If you try to open the file, you will get an alert that says “[Document] can't be opened right now.”
If you get this alert, ask the owner of the file to save it as a single file and send it to you.