Help:Deleting a page
Normal users cannot permanently delete a wiki page. This is a deliberate design feature, and is an important part of why wikis work. Every kind of editing operation can be reverted by any other user, and that includes resurrecting deleted content. It doesn't cause significant wasted space; and with nothing but a 'delete' label, the page is effectively deleted anyway.
Deleting a page is, on the other hand, a straightforward operation for anyone with sysop or admin permissions: it allows to semi-permanently remove a page from the wiki, until a sysop undeletes (restores) it with the same ease. Typically sysops might look for delete labels, and do a proper delete on these pages, after a period of time. If for some reason you need a page to be deleted more quickly than that, you will need to contact a sysop to request this.
Sysops should also be aware of the general advice given on when not to delete a page: in particular, there are many situations where a deletion is too drastic. For example, a redirect is often more appropriate.
Use the 'delete' action
Sysops should see a 'delete' tab or action menu option at the top of every page. Click this to delete the page. When using browsers which support keyboard shortcuts, you can also use (Control-Alt-D). You will be asked to confirm, and to supply a "Reason for deletion". This is a short textual description of why the page is being deleted. Your action will appear on the recent changes display, and in the deletion log (Special:Log).
To undelete a page you must navigate to the exact page name of the page. You can find this in the deletion log (Special:Log) if you dont remember it.
You should then see a link to "View or restore n deleted edits". Tick the box next to the revision you wish to restore.