You can make a link to another wiki page simply by stating the name of the wiki page. For example, the name of this page is MarkupInternalLink.

The name of a page has a special syntax known as a WikiWord. A WikiWord starts with a capital letter and has at least one more capital letter in it. Between the capitals there must be lower case letters or numbers. There cannot be two capitals in a row.

Thus:

Wiki Words	Non-Wiki Words
BobMartin[?]	Bob
RobertCecilMartin[?]	hello
ObjecT[?]	Object
NumbersLike123AreAllowedNow[?]	Butnotlikethis123

If you place a WikiWord in the markup text, but no such page exists, then you will something like this on the page:

NoSuchWikiWord[?]

If you click on the question mark it will create that page for you, and allow you to edit it.