Hello poppacas. Welcome to MobileRead.
The Kindle is essentially a simple device. Turn it on. Load a book. Select the book. Read. Turn pages. Turn it off.
Every reader that I know about behaves exactly the same.
Now, with the Kindle, you can do some more advanced things like change the font size, set a bookmark, highlight text, and even write a note "in the margin". Again, all the readers I know of implement multiple fonts and bookmarks. Not every one has a highlight or note function.
Once you turn on the cellular antenna -- if you're in the USA with a Sprint service area -- then you can connect to the Kindle store at Amazon.com and browse the new books, bestsellers, recommendations for you, and Kindle news. You can buy a book from the Kindle and Amazon will ship the book to you over the cell connection directly into your Kindle. (Of course, you can also do your buying and downloading with your browser and push the book into the Kindle over the USB connection.)
There is an experimental browser in the Kindle and you can use it to access some web sites -- it works best with those systems that have a mobile portal optimized to hand-held devices. You can get the
MobiPocket Download Guide from MobileRead and then use it to download books from MobileRead into your Kindle over the cellular connection. You can get the
Kindle Download Guide from Feedbooks and use it to download their books directly into the Kindle.
The network connectivity is not unique to the Kindle, but there are fewer book readers that do have the ability to connect to servers, and the Amazon store is the only one I know of that has a built-in interface for shopping, buying, and delivery of books direct to the device.
A couple of other features that the Kindle shares with some other readers -- the ability to play music and/or audio books. The Kindle's support for audio books is limited to books from Audible.com. Yes, you can put MP3 files onto the Kindle, but it doesn't support any form of a playlist, so it's difficult to "read" an audio book in MP3 format when you can't rely on the player to play each file in the correct order.
Personally, I don't use the audio components in the Kindle (or in the Sony, for that matter) since I have a tiny, full-function MP3 player with 16G of storage. I also only use the network function in the Kindle for shopping at Kindle. Every once in a while I'll use one of the download guides to grab a book from MobileRead or Feedbooks -- but I mostly use those as nicely formatted "library catalogs".
The wiki and forums here have lots of information about the various brands (and models within brands) and the functions that they provide. Which ever reader you choose, you're in for such a treat.