I've been wondering this for awhile. Do you have to have a separate file on a server that defines the xml tags, and then use them in a page after you've linked to the .xml file or something? (Like how css works)

And it's used for security right? Like if a certain company uses a .xml file and defines some tags, the only people who have the .xml file can read exactly what the tag is, right? How is it used in today's webpages?

Thanks for the responses.

XML was really confusing to me too when it first came out as everyone touted it as some great technology, however I soon found out it is nothing more than a way to structure data.

A sample XML file may look like this...

<?xml version="1.0" encoding="ISO-8859-1"?>
<source>

	<url>http://www.webmaster-talk.com</url>

	<thread id="28214">
		<title><![CDATA[? about selling links please]]></title>
		<author><![CDATA[Boston_JM]]></author>
		<date>04-23-2005</date>
		<time>01:05 AM</time>

	</thread>
	<thread id="28213">
		<title><![CDATA[Shooting Forum - ShootingTalk.com]]></title>
		<author><![CDATA[HitSnapper.com]]></author>
		<date>04-22-2005</date>
		<time>11:56 PM</time>
	</thread>
	<thread id="28212">

		<title><![CDATA[Banner Ad on Webmaster Forum]]></title>
		<author><![CDATA[HitSnapper.com]]></author>
		<date>04-22-2005</date>
		<time>11:51 PM</time>
	</thread>
	<thread id="28211">
		<title><![CDATA[help plz!!]]></title>
		<author><![CDATA[cpfreak23]]></author>

		<date>04-22-2005</date>
		<time>11:41 PM</time>
	</thread>
	<thread id="28210">
		<title><![CDATA[Hidden Field Help..]]></title>
		<author><![CDATA[cpfreak23]]></author>
		<date>04-22-2005</date>

		<time>11:14 PM</time>
	</thread>
	<thread id="28208">
		<title><![CDATA[What am i doing wrong?]]></title>
		<author><![CDATA[spence]]></author>
		<date>04-22-2005</date>
		<time>10:42 PM</time>

	</thread>
	<thread id="28207">
		<title><![CDATA[How exactly does one make use of XML?]]></title>
		<author><![CDATA[Zeal]]></author>
		<date>04-22-2005</date>
		<time>10:08 PM</time>
	</thread>
	<thread id="28206">

		<title><![CDATA[Buying Advertising On Finance Related Sites]]></title>
		<author><![CDATA[TalkingWorld]]></author>
		<date>04-22-2005</date>
		<time>09:59 PM</time>
	</thread>
	<thread id="28205">
		<title><![CDATA[Add your link, no linkback required.]]></title>
		<author><![CDATA[PortProphecy]]></author>

		<date>04-22-2005</date>
		<time>09:44 PM</time>
	</thread>
	<thread id="28204">
		<title><![CDATA[PR update not effecting all toolbars]]></title>
		<author><![CDATA[AnthemIT]]></author>
		<date>04-22-2005</date>

		<time>09:30 PM</time>
	</thread>
	<thread id="28203">
		<title><![CDATA[Space On My Server]]></title>
		<author><![CDATA[MonsterCreek]]></author>
		<date>04-22-2005</date>
		<time>09:13 PM</time>

	</thread>
	<thread id="28202">
		<title><![CDATA[Linguistics-related]]></title>
		<author><![CDATA[italicus]]></author>
		<date>04-22-2005</date>
		<time>08:45 PM</time>
	</thread>
	<thread id="28201">

		<title><![CDATA[Link exchange with software related site PR5]]></title>
		<author><![CDATA[Dranix]]></author>
		<date>04-22-2005</date>
		<time>08:43 PM</time>
	</thread>
	<thread id="28200">
		<title><![CDATA[Free PHPBB Forum Hosting from NetFreeHost.com]]></title>
		<author><![CDATA[flashweb]]></author>

		<date>04-22-2005</date>
		<time>08:33 PM</time>
	</thread>
	<thread id="28199">
		<title><![CDATA[Desert Realm Fantasy and Scifi Search Engine]]></title>
		<author><![CDATA[azkul]]></author>
		<date>04-22-2005</date>

		<time>08:26 PM</time>
	</thread>

</source>

Infact, this is the XML data feed from this forum at the exact moment that I snagged it. Now in this form it really is meaningless, however if I use a programming language to parse that text and extract the information from inbetween the tags then I can get some use out of the data.

As far as how it is used in webpages, well there are many uses, all created by end users. XHTML is a way to force the XML standards onto HTML.

For a more indepth explanation of XML see this website...http://www.w3schools.com/xml/default.asp

Have fun, you have a lot to learn.