Web pages and Browsers all work differently. They either have a certain code which keeps them simple, or a code which makes them damn right complicated. This is what makes today's internet.
The information which goes into pages really counts, so it can compute into our browser and make sense to us, rather then bunches and bunches of text which means absolutely nothing. During the big internet boom in the 90's, all a web page was, was full of links (Hyperlinks) which guided you to certain folders or spots with information. Now, you can only see this if you would like to file share on a web page rather then sending the file, or use it for storing information as you create a website.
Codes and Languages which make up the Internet/Webpages
HTML
HTML, or Hypertext Markup Language is possibly the most common language used for web page make up, but also the basic building blocks which make up a normal web page. HTML is laid out in tabs or tags which hold information for a certain command (For example; To make text
bold in the coding for a website you would have to use tag "<b>" write in your text and then close the tag with "</b>" when you have finished the line you want bold). HTML is the code which makes web pages simple and understandable for viewers.
JavaScript
JavaScript is a proto-type based language which runs on first class settings and multiple languages, so it is a very loose and simple language to learn. JavaScript is mostly used to load up applications (which come from outside a web browser) inside a web browser window (Such as PDF files) but the language can often be used to load up Widgets for your desktop or make a Site-Specific browser load up onto any other browser.
PHP
Originally, PHP (Hypertext Processor) was just designed for web development purposes to produce sofisticated and dynamic web pages. Now, PHP is embedded into HTML to create what is known as a pure web page as it help sustain and make a web page look pretty. PHP can be deployed and used onto many web space servers and on almost every single operating system and platform without no money fee. This is because it is a free software which can be used in many places for your benefit if using to create a web page or website design.
XML
Quite like JavaScript, XML (Extensible Markup Language) where it encodes documents in a machine-readable form. Although, this isn't for Web Browsers, but for the computer its self. This means it keeps a user posted on something which is being updated countlessly on a daily/monthly or even yearly basis. An easy way to show an XML feed is RSS feeds which is something commonly used on the internet to update whether a new web comic has been released or that a new game has just hit the internet and there's loads of reviews about it. Other then that, items such as ATOM, SOAP, XHTML have XML embedded into it as well.
DOM
DOM (Document Object Model) is possibly one of the few oldest web languages and was the main key to the Browser Wars. A specific web browser is not acquired to use DOM, however, JavaScript is dependent on DOM to function and script a web page properly, sorting the HTML and Browser to render and work as one. (The unfortunate side is that different browsers use different HTML states, during the browser wars, which made the DOM useless in some areas.)
JAVA
The most popular language on the internet, to date, JAVA is used to power things like Flash files, Quick Time files, Chat Scripts etc. onto the website or web browser its self. Even thought the language its self is quite hard to manage and use, it's very good for staging and then running applications for some ones benefit. For example, free online drawing programs such as Oekaki's (Japanese/European drawing sites) and Paint Chats all run on JAVA powered engines, so it's a known thing to many artists.
CSS
Embedded and coded in between HTML brackets and codes, CSS (Cascading Style Sheets) is what makes your normal web page look pretty. The language its self controls the colours and the settings that HTML can't provide its self, as well as certain functions where it can code a webpage so that every webpage has the same formatting as the last, which makes it simpler for the designer to get pages done as fast as possible. It's basically a code which makes things which are much more harder to manage, much more easier and simplistic.
FLV
The abbreviated term for Flash Video, it's a file format which now uses Adobe Flash Player to play footage on the internet. It is viewable on most operating systems, accept for iPhones/iPods, which have a distinctive way of coding in its self, and much more complex then what FLV provides. FLV supports two different kinds of file share, in which both types of files are bitmaps but unfortunately colour is broken down to make the file run faster as well as being compressed.
SWF
SWF is a file format which is much more sophisticated then FLV files, and can contain much more bigger files with better quality. This means that it would be more efficient to have it on a website to make it more appealing. Unlike, FLV files, SWF's are out to impress, but uses the same software (Adobe Flash Player) to run the clip or file. Normally SWF is used for animations and vectored images.