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.