The Progress Indicator is at the bottom of every item you read on your Kindle. It tells you where you are (percentage) in the book or article, and also gives you a numeric location of where you are reading, so you can easily find a particular section or reference it to your friends. Locations are the digital way to replace pages in a book. A particular location will always be the same on a Kindle book, no matter what size text the reader chooses to use or if they wish to adjust the number of words per line to make reading easier.
Flipping through the pages...
No, you can't really do that, but if you look at your progress indicator at the bottom of your Kindle book, you might (in most instances) see a bunch of little dots. These are section indicators, and you can use the right or left buttons in the 5-way controller to navigate forward or back in your book quickly. These little section indicators may take you forward a chapter at a time, or an article at a time (like in a blog). It depends on the reading material and how it was formatted. Some don't have any sections at all, and some books are very well equipped.
The 5-way controller on the Kindle 2 is a little different from the latest Kindle. The Kindle 2 is more of a toggle switch you can move up, down, left or right, then press in on it to make what you have selected happen. The 5-way controller on the latest Kindle is a flat button in the center, surrounded by slivers of buttons, one at the top, right, left and bottom. Press the buttons surrounding the center flat button to make your selections (or move forward or back from various locations in your book), then press the center button to make things happen.