XML and RSS

To be honest, I am just catching up new trends in the internet,
like Blog, podcast, XML, which is written in the Chapter 8 of the textbook.

For example, I did not catch the meaning of the word "XML" in the textbook (P.387)
so that I went to the internet and searched the definition.
I went to the Wikipedia, which the professor mentioned in the class.

http://en.wikipedia.org/wiki/XML

If my understanding is correct, XML is like an HTML, a language with tags used in the internet.
We can use any tag we want with definition and we can use like an database.
I understand that it is used at least in the blogs and RSS.
This contains example of XML for news article.

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


P.S. Also, I found there is a online e-marketing education site.
I am sure it will help us understanding more of the textbook.

http://www.businesslink.gov.uk/bdotg/action/layer?topicId=1075384972