Isn't XML the same as HTML?

No, XML is not the same as HTML although there are some similarities. Why are there similarities? The reason why is that both XML and HTML are derived from SGML (Standard Generalized Markup Language). What are those similarities? Well, for example, both XML and HTML have similar syntax and use bracketed tags.

The main difference between XML and HTML is that the former can define new applications and the latter can't. Take a look at the diagram in this page to see the relationship between XML and HTML.

Below is also a code snipped of XML that will help you see the similarity between XML and HTML.

<contact-list id="file790">
<name>Company Inc.</name>
<address country="Australia">
<street>7301 Suddley Road</street>
<city>Some City</city>
<postal>19994</postal>
</address>
</contact-list>

As you can see, the similarities are obvious. Keep in mind though that there is more XML than the few tags you saw above. Also, note that the purpose of XML is not to render HTML and other languages obsolete.

Is XML here to stay?

Everything I've seen and heard seems to point in that direction. Some authoring tools such as HomeSite 4.0 and Cold Fusion 4.0 already support XML. If you'd like to learn more about XML and the new recasting of HTML in XML (XHTML), visit the W3C's web site.