Names of pages have to ?LookLikeThis. It's called a WikiName. If you write a word that ?LookLikeThis, it will be automatically turned into a link. You will find more details about this in HelpForBeginners.
The following pages describe the elements (wiki markup) you can use to get special formatting effects:
HelpOnFormatting - general text formatting rules
HelpOnLinking - external hyperlinks and inline images
HelpOnHeadlines - section headings
HelpOnRules - horizontal rules
HelpOnLists - lists and indented sections
HelpOnTables - tables
HelpOnIcons - how to insert a graphical icon
HelpOnMacros - system macros
Variable substitution - which variables are substituted (like @SIG@, @MAILTO@ ...)
HelpOnParsers - data processing parsers (replaces Processors)
HelpOnEditLocks - how to behave correctly when edit locking is activated
HelpOnCategories - how to group wiki pages
/SubPages - how to group together related information
To experiment with wiki markup, go to the WikiSandBox and then click on "EditText" at the bottom of the page. Use your browser's "open a new window with this link" feature on the word "WikiSandBox", so you can keep the help pages open side-by-side to the editing window.