It's pretty simple.
http://amzn.com redirects to
http://amazon.com
And there are a whole bunch of service names which you can put after either one, to redirect to the feature page.
I know
http://amzn.com/manageyourkindle
http://amzn.com/account
http://amzn.com/prime
As well as things like:
http://amzn.com/kindle
http://amzn.com/kindlepaperwhite
http://amzn.com/kindledx
And more, some of which I forget. Usually,
I guess them based off of the name, like:
http://amzn.com/kindleunlimited
and also, if it is multiple words, like
http://amzn.com/manageyourkindle
I know it can be shortened to the abbreviation
http://amzn.com/myk
so I tried that for Kindle Unlimited too.
Also, there is http://amzn.com/{ASIN} which when you substitute {ASIN} with the Amazon product ID redirects to any product page. The Kindle Paperwhite (
http://amzn.com/kindlepaperwhite) is also
http://www.amazon.com/Kindle-Paperwhite-Resolution-Display-Next-Gen/dp/B00JG8GOWU/
The Product ID (ASIN) is B00JG8GOWU which then becomes
http://amzn.com/B00JG8GOWU
I have gotten fairly good at guessing the name of things. I even figured out, after some effort, the Win8 app:
http://amzn.com/kindleforwindows8
Which was some effort.

I kept trying to stick the word "app" or "metro" in somewhere.
They seem to have links for most things, and they are usually
mostly obvious.