Ebooks are computer files, or some other type of electronic format. We have a merchant here on the forum that sales ebooks on CD -
survival Ebooks. That way you have the files in a portable format.
"What" you can do with these Ebooks? Lets talk about that for a minute.
Lets say that your going on a hiking trip, you can find the pages on navigation, print them out and put those pages in with your TOPO maps. If you need a reminder on navigation, you have a cheat sheet on hand. So instead of carrying the full sized survival manual with you, you can just bring some single pages.
Another thing - if you have a good printer, you can print out some of the pages and put them into a binder. That way you have a physical backup of important information. And you do not have to rely on a computer if you have a printed copy.
Ebooks are a lot cheaper then full sized survival manuals. Yea printed books are nice, but ebooks are more flexible. If you want a hard copy of one page out of a book, you have to have a scanner. With an ebook all you need is a printer.