Aliases allow you to set any URL that returns the contents of any resource available in the /public for your blog.

The target of the alias must be an element of the media manager's blog. The URL alias will deliver the target without revealing the real media URL.

Otherwise, it's a classic redirect to the destination of the alias.

And if in addition you have chosen to create an alias disposable, it self-delete after the first access to the URL in your browser.

Destination
The destination of the alias is an existing item in the library of blog. This field is required.
URL (alias)
The alias is the URL that you create, not the blog URL. URL aliases called "about" will be recognized when someone called http://yourblog/about.