When you save to disk the book is stored in a folder by author's name. Within that folder is a folder for the book. Within that folder is the book by file type(s), OPF file and I think the book cover file.
You can easily send the folder of the book containing the above to yourself, a usb storage device, cd, etc. or another person via email as attachments.
It is quite easy to do. The options for sending to device are failry wide and easy to use. If you're not sure how it's going to work practice by creating a folder on your computer and send the book to it using Calibre and the varied send to device options.
You could also go through the more laborious method for copy/paste the file/folder from the Calibre library found in explorer but the send to device method via Calibre is much easier.
You are sending a copy of the book...not the book itself.