What is the difference between XML, HTML, and XHTML?

[masonjade]

What's the difference between XML, HTML, XHTML, Apache, MySQL, javascript, SSI, PHP, and CSS? I'd like to start learning how to make webpages, learn more about servers and networking, and be able to do something with the knowledge. I'm learning C++ now, but I've heard that HTML is far more simple. So...can someone fill me in on all of these different things, their differences/similarities, what you can do with them, what they are, where I may have run into them or seen them in use before, how I'd go about learning more about them, or using them (if that applies, example if something is a programming language). I'm a bit clueless now as you can see, so I'd like some info. Thanks!