Permalink means permanent link. It is a stable URL that takes you directly back to a specific webpage or article.
Many of our databases offer permalinks which add our proxy (to authenticate you/prompt you to log in) to access the material again later. Permalinks are important to collect if you have research you want to get back to. Many of the urls in the address bar are session-specific, and will have timed out if you try to access the material again using them. Links sometimes timeout because it is tracking your use or navigation on the page, for example.
Copying the url in the address bar is not always a safe bet. It's better to look for a permalink icon (often a link icon like this:🔗) or share feature to grab the permanent url. This will be in different places depending on the site/database.
For example, this is what it looks like in our catalog:
In the databases, such as Gale, it may be called a "Get Link" or "Bookmark" option:
