Page names on Wikimedia Commons give an indication as to what is contained on the page. A page may be part of the actual content (such as a gallery, category or multimedia file) or for the administration and maintenance of Commons.
Some pages have a prefix to indicate which Commons namespace the page belongs to. Gallery pages do not have a prefix but others may begin with "File", "Category" etc. The namespace forms part of the en:URL as well as being shown at the top of the page. The "page name" of this page is Page name; to reach it you need to specify the "full page name" including the namespace, i.e. Help:Page name.
See also 
- Commons:First steps/Upload form#4. Set an appropriate file name - basic guidance
- Commons:File naming - proposed guideline
- m:Help:Page name - full technical details including technical restrictions on page names, on Meta-Wiki