What is XML ?
XML (Extensible Markup Language) is a markup language (remmber HTML?) designed to store and transport data. If you already familiar with HTML, you may notice that the syntax of XML and HTML is pretty close. But XML is often used to represent data and the child is enclosed by their parent.
Sample of XML Formatted Text :
<?xml version="1.0" encoding="UTF-8"?>
What is Minification (from Minifier) ?
Minification is the process of removing all unnecessary characters from the source codes without changing their functionality or behaviour. So, the size of your code will be reduced without changing the result of the code.
Minification can remove few things from source code such as spaces and newlines. Or even can change the structure of the code while maintaining the same result (this example is quite extreme, but possible. The process can be quite the same as in the compiler).
The drawback of minification of course the code can be harder to read, thats why minify can be called uglify.