SharePoint
wiki links only work within one site, and they cannot be
added by clicking a button. Instead the wiki link syntax
has to be typed in.
But with wiki links you can achieve things that are difficult
to do in other ways. Peter Kalmstrom, CEO of kalmstrom.com
Business Solutions and Microsoft certified SharePoint specialist,
shows some examples in the demo below.
Double square brackets
Wiki links are always surrounded by double square brackets,
and when you type the first two brackets on a SharePoint
page in edit mode, you will be shown a list of the site's
pages, lists and views. Select one of the options and add
the closing brackets, and a wiki link is created.
Peter shows seven different ways to manipulate and work
with wiki links. Note that he uses the TAB key when he links
to a document and a list.
Create a link to an existing page.
Create a link to a non existing page and let SharePoint
create the new page.
Create a link to a library.
Create a link to a document
Modify the anchor text of a link.
Create a link to a list.
Create a link to a list item that opens the item
in a new window on top of the SharePoint page where
the link is placed.
SharePoint
wiki links only work within one site, and they cannot be
added by clicking a button. Instead the wiki link syntax
has to be typed in. 
Wiki links are always surrounded by double square brackets,
and when you type the first two brackets on a SharePoint
page in edit mode, you will be shown a list of the site's
pages, lists and views. Select one of the options and add
the closing brackets, and a wiki link is created. 