How do I get these files on my e-reader?
This depends on which e-reader you have, but it should be simple in each case! If it is a download directly from the store of the device you have, you already know how it works, of course. If it is from a publisher or author website, it may be slightly more complicated – but only slightly.
For a Kindle connected to a PC: You should download and save the “Mobi” format file for the book you want. Then connect your Kindle to the PC via its USB cord. An “AutoPlay” dialog box should open, and you can select the “Open folder to view files” option. This will open your Kindle as a drive on your computer. Several folders will be visible, including one named “documents.” Simply drag the .mobi file from wherever you saved it into the “documents” folder. Disconnect your Kindle safely by using the “Safely Remove Hardware” option (available from the bottom right-hand side of your taskbar on most modern Windows installations), and voila! Your book or story will be ready to read when you next start up your Kindle.
There is also ebook management software available that can make all of this even easier. I recommend calibre, which has clear instructions for use on its site and has made my free e-reading life much simpler.
Why would publishers or authors give their books away for free?
Generally because they know that obscurity can be an author’s biggest enemy and that everyone loves free stuff. They’re also probably hoping that, if you like the work you read for free, you might buy a paper copy, buy some of their other work, and/or recommend their work to friends.
What’s the deal with the tags?
I’m working on making them as organized as possible, but generally, if a post is tagged with file formats, you’re downloading a file directly, which you will have to manually transfer to your device. If it’s tagged with an e-reader type, the download will come from the store directly. Note that store downloads are more often time-limited than file downloads.