Many article titles are disambiguated with parenthetic qualifiers, like this: [[Self (psychology)]]. But when you want to include such a link in the body of an article, this would look rather awkward. So all you have to do is use the "pipe trick", like this: [[Self (psychology)|]]. Notice the "|" character stuck in there at the end of the link? That makes the link look like this: Self, without having to type the name of the link after the pipe!
This trick also works with namespaces, so that [[Wikipedia:Tip of the day|]] (again notice the pipe character) displays like this: Tip of the day.
