Permalinks are simply the permanent URLs of your WordPress posts and pages.
This is the permalink of this post.
Default WordPress permalink structure is based on the page/post name and date when the page/post was published.
But this can be easily altered.
Here is how to change the default permalink structure on WordPress:
To change a permalink of an individual post/page look at the right sidebar options on Gutenberg:
In WordPress Classic Editor, this option is right under the page/post title