page name
The page name is a string that Pm Wiki uses to refer to a page - i.e. it names the page. This could also be considered a handle for the page. The variable for the page name is simply called {$Name}, which for this page is Glossary. Note that there is no whitespace in page names, and by default Pm Wiki capitalizes each word in a page's name. There is however a variable {$Namespaced} where spaces have been inserted, e.g. for the page WikiSandbox this variable would be Wiki Sandbox.
Note that Pm Wiki also uses the page name to locate per-group and per-page customization files in the local/ subdirectory. For example, browsing Main.WikiSandbox would cause local/Main.WikiSandbox.php and local/Main.php to be loaded if these files existed.

Page URI
Page names are used in URIs to tell Pm Wiki which page is to be loaded or acted upon. The normal form of a page URI is usually one of these two
http://www.example.com/pmwiki/pmwiki.php?n=Main.WikiSandbox
http://www.example.com/pmwiki/pmwiki.php/Main.WikiSandbox
Note that various aliasing and rewriting tricks can be used to modify this, but Pm Wiki expects to obtain a page name from the parameter 'n' or from the PATH_INFO component following the URI of the script (pmwiki.php).
Note that the parameter 'n' takes precedence over PATH_INFO if both are available.

Page file name
The page file name is the name of the file that normally stores the data of a page in the directory wiki.d/. This file name is normally built directly from the page name.

full page name
The full page name consists of a group and a name, e.g. Main.WikiSandbox. The variable for the full page name is {$FullName}, which for this page is Pm Wiki.Glossary. Similarly, the variable for the group is {$Group} which here is Pm Wiki.

A page link is something that is used to generate a link to a page. For example, the markup [[wiki sandbox]], [[(wiki) sandbox]], WikiSandbox, Main/WikiSandbox, [[Main/wiki sandbox]], [[Main.WikiSandbox | click here]], etc all specify a link to the page 'Main.wikiSandbox'. In each case Pm Wiki uses the context of the link to generate a page name from the page link -- normally by capitalizing each word found in the link and stripping any characters that aren't considered valid in page names.
A page title is the title element of a page, i.e. what is usually shown above the page and in the browser window's name. This title is normally set via the directive (:title:), but if no such directive is given the title will be automatically generated from the page name. The title of a page is accessed via either the variable {$Title} or the variable {$Titlespaced}. The latter differs in that it uses the spaced version of the name.