Manual:Page title

A page title is the title of a page. it is stored in the page table. When one is specifying a certain page by typing it into the search box, or putting it in an article as a wikilink, the input consists of a namespace (or no namespace, if it's mainspace) followed by a colon (optional if it's mainspace) and then the database key. E.g., Manual:Page table specifies the Manual: namespace and the Page table database key.

Invalid page titles
The following are not valid as page titles:
 * Base names beginning with a lower-case letter (in any alphabet), depending on the setting of $wgCapitalLinks. Note that a title can be displayed with an initial lower-case letter, using DISPLAYTITLE or the lowercase title template.
 * Titles containing the characters # < > [ ] | { } _ (which have special meanings in Wiki syntax), the non-printable ASCII characters 0–31, the "delete" character 127, or HTML character codes such as &amp;amp;. Note that the plus sign + is allowed in page titles, although in the default setup for MediaWiki it is not. This is configured by setting the value of $wgLegalTitleChars in LocalSettings.php.
 * Base names beginning with a colon (:).
 * Base names equal to "." or "..", or beginning "./" or "../", or containing "/./" or "/../", or ending "/." or "/..".
 * Base names whose length exceeds 255 bytes. Be aware that non-ASCII characters may take up to four bytes in UTF-8 encoding, so the total number of characters you can fit into a title may be less than 255.
 * Titles beginning with a namespace alias (WP:, WT:, Project:, Image:, on Wikipedia). For example, the name Project:A-Kon is not possible if Project: is set set as a namespace alias.
 * Titles beginning with a prefix that refers to another project, including other language Wikipedias, e.g. "fr:" (see Interwiki linking and Interlanguage links). For example, an article about the album "Q: Are We Not Men? A: We Are Devo!" cannot have that exact name, as the "q:" prefix leads to Wikiquote. (The restriction includes the prefixes "w:" and "en:" that refer to English Wikipedia itself. This self-reference restriction does not apply on all projects; for example, Wikiquote supports titles beginning "Q:".)
 * Titles beginning with any non-standard capitalization of a namespace prefix, alias or interwiki/interlanguage prefix, or any of these with a space (underscore) before or after the colon. For example, it is not possible for a title to begin "HELP:", "HeLp:", "Help :" or "Help:_".
 * Titles consisting of only a namespace prefix, with nothing after the colon.
 * Titles beginning or ending with a space (underscore), or containing two or more consecutive spaces (underscores).
 * Title cannot contain 3 or more continuous tildes.
 * A title can normally contain the character %. However it cannot contain % followed by two hexadecimal digits (which would cause it to be converted to a single character, by percent-encoding).

Note also that it is not possible for editors to create page titles beginning with the virtual namespace prefixes Media: and Special:.