permalink are short links that will be permanently accessible even if the page is moved
A generated permalink is a link that uses the page id as page path
As the id is guaranteed never to change, it's the real / true permalink.
<permalink/>
A generated permalink performs a permanent redirection to the page url
A named permalink is a link that uses the canonical as page path
Note that a canonical is not a true permalink as it may be modified (It should not, but you never know)
<permalink named strict="false"/>
A named permalink performs a permanent redirection to the page url.