[Owen]

The thing about XML is that it lets you describe data in a pretty much universal format. You use XML all the time, for example, HTML is a form of XML, where the page content is defined in a structured format.

The usefulness of XML is pretty much taken for granted nowadays, but before it was around, you would use proprietary formats to communicate from one system to another, most of which was archaic and very few of those formats were human readable.

An appreciate of XML is important, though you may not need it right away if you're building simple applications. However, when you start talking about integrating different services, using AJAX or even generating HTML in a structured way, you need to start getting your hands dirty with XML. Luckily most languages today have XML parses built into them letting you quickly serialise classes into XML, or traverse XML nodes efficiently for example, which really cuts down on the time it takes to build things.