Minor rewording of priority filter explanation

Minor rewording to make it more clear which "priority" features are
being talked about.

Also updates links to be relative.

doc/book/writers.md

@@ -540,11 +540,11 @@ which means that:
 When you add a writer to the logger, you can set its priority as a second
 argument. This priority is the priority in the queue of all writers of the
 logger. It can be any integer, and the default is `1` (`\Zend\Log\Logger::ALERT`)
-for the writers. Bigger the number, bigger is the priority. A writer with a
-lower priority will  be triggered later, so `ALERT` is triggered after `DEBUG`.
-For  details on the list of the priorities, see [Using Built-in Priorities](https://docs.zendframework.com/zend-log/intro/#using-built-in-priorities).
-
-This priority should not be mingled with the filter [`Priority`](https://docs.zendframework.com/zend-log/filters/#available-filters).
-In fact, this is the severity. It means that the writer will output the message
-only when the filter is lower or equal (by default) to the priority (the biggest
-severity is 0).
+for the writers; the bigger the number, the higher the priority. A writer with a
+lower priority will be triggered later, so `ALERT` is triggered after `DEBUG`.
+For details on the list of the priorities, see the section entitled [Using Built-in Priorities](intro.md#using-built-in-priorities).
+
+This priority should not be confused with the [`Priority` filter](filters.md#available-filters),
+which determines if a message meets a _severity_ threshold. When a `Priority`
+filter is attached, the writer will output the message only when the filter is
+lower or equal (by default) to the priority (the biggest severity is 0).