'sA-dE . com

Found a really good (in my opinion) introduction and Tutorial to RSS and Web Feeds in general at:

http://blog.contentious.com/archives/2003/10/18/what-are-webfeeds-rss-and-why-should-you-care

Other sources of information I came across searching on "RSS Feed what is it" on the internet turned up the following two (as well as many others) but not sure if they are more technical than what you are looking for:

http://www.faganfinder.com/search/rss.shtml#what

http://www.xml.com/pub/a/2002/12/18/dive-into-xml.html

As for targetted ads... basically I believe they require the user to have provided some level of information about themselves somehow in some format. Generally, when you submit information to a web site explicitly by filling out a form or application, you've also accepted some sort of privacy statement before committing the data, that talks about how the information you provided will be used. Based on the information the web site knows about the user whether it was provided explicitly(may be as simple as a zip code for location-based targetting, or more complex like your age or birth date, or your occupation, or your hobbies, or previous purchases you've made at that same web site) or perhaps was provided without your explicit input (eg the referring URL from which you arrived at the web site), the web site will attempt to display ads on the web site that are likely more relevant to you based on the information it has about you.

Here's a link to Amazon's Privacy Statement:

http://www.amazon.com/exec/obidos/tg/browse/-/468496/102-8450146-6056962

It gives you a very clear explanation of what information it gathers about you - how it gathers it (you provide it yourself, or it learns it some other way) and how it uses that information. Much of that information is used to do the "people who bought this item also bought X" and other personalization features.

reading that might help you understand a bit more how those personalization features can work.