reading notes 11/8

Intro to XML: Seems like more than an intro to me. I found this article quite confusing, except the parts that are similar to HTML, which I finally feel like I'm getting a hang of.
This part confused me:

"It is important to note, however, that XML is not

• • a predefined set of tags, of the type defined for HTML, that can be used to markup documents
• • a standardized template for producing particular types of documents."  Can anyone "dumb-down" this "important" note for me?
  
  Also, what is boilerplate text? I feel like I could use more examples
  
  
  Survey of XML Standards: Not much better. I'm still confused. I feel like that whole thing was over my head. I don't think I understand the difference or connection between XML and HTML.
  
  
  Extending Your Markup: The intro to this read my mind! I don't think the article lived up to the intro. I feel like I keep reading the same thing again and again, but not getting it. I don't understand the child/siblings bit.
  
  
  XML Schema Tutorial: I really like these tutorials. I think this was the most useful article of the bunch. It's still a strange concept to me, but I find the examples useful.