A permalink is a static URL that links directly to an online resource that you can use to go directly to the resource without needing to recreate your search.
But, can't you just copy the URL at the top of the page and save it? Unfortunately, that doesn't always work. A number of library resources are generated using dynamic, database-driven websites that do not automatically have a dedicated URL that you can copy and paste from your toolbar into your document. After a time, these URLs will become disabled and unusable. The only way to guarantee access to an article, video, etc. is to use a permalink when linking within another document.
There are several different names that products use to indicate a permalink. You may see the words Permalink, Bookmark, Permanent Link, Stable URL, etc., but they will all provide you with the same information.