!Hiya! And welcome to Wiki!
WikiWiki is Hawaiian and means "quick". The original idea of WikiWiki was to create a collaborative, fast environment which would still be persistent.
Anyone can contribute, even anonymously. Yes, you can delete what other people said, and even delete whole pages, but surprisingly, wiki [does work|WikiWikiWeb:WhyWikiWorks].
When editing, you can easily create (and you should create) hyperlinks by just putting the word in square brackets, [[like this]. If the page you are referring to does not exist, the resulting page will show the name underlined, with a following question mark. Like this: [ThisPageDoesNotExist]. (Please don't foil this example by creating that page...)
WikiNames that contain spaces or underscores are crushed together and capitalized, so that [[This is a link] becomes [[ThisIsALink].
Wiki is and should be simple. This is why there is no need for complex HTML. You can get some effects, such as __bold text__ and ''italics'', but nothing very complex. Layout is the problem of the Wiki itself. There is more information in [TextFormattingRules].