WP:Prefix

You may be looking for:

Special:PrefixIndex — search for pages whose titles match a given text string at their beginning (see also Wikipedia:Special:PrefixIndex)
Wikipedia:Searching — searching more generally, including the {{code|prefix:}} query operator
Wikipedia:Namespaces — about the prefixes prepended to page titles for non-articles
Help:Interwiki linking — all the short codes ending with {{char|:}} you can put in wikilinks (these kind)
Special:Interwiki — Full list of interwiki prefixes currently usable on this project
Wikipedia:Templates — templates and template syntax, including the prefixes you can use