Here are the options you see in the
Publish tab:
Web — Publish to Web puts your books or collection on BloomLibrary.org so that other people can read them, download them to their devices and share them with other people.
BloomPUB — This option allows you and others to view your books on phone apps (Bloom Reader and Reading App Builder apps) and on Windows using BloomPUB Viewer.
They offer many advantages over ePUBs, including WYSIWYG fidelity and the full range of Bloom digital book features.
See:
Make All BloomPUBs from Collection (a Bloom Enterprise feature).
ePUB — Publish as ePUB and save an ePUB file so your book can be used in various ePUB readers.
Dropbox is one handy way to copy your ePUB files to your device (e.g. phone). Save the ePUB file to your Dropbox folder. On your phone, open the Dropbox app and select your book.
Google Drive and Microsoft's One Drive are other services you should consider.
SHAREit is a cross platform app for sharing data.
Audio or Video — Publish as Audio or Video to make an audio or video book. Then your book is available as an Mp3 Audio file, or a video for YouTube, Facebook or feature phones.
PDF & Print is not actually a digital publishing option, but you can save your book as a *.pdf file.
https://play.google.com/store/apps/details?id=com.microsoft.skydrive&hl=en_US