Creating a refined view of a panel
Refiners are designed to let you modify a panel that by default shows every type of item, and customise it so that it only displays a certain type of item.
For example, you could create a refiner on the users panel that showed every user whose name begins with the letter 'A'.
Refiners may also take inputs to filter on. So slightly more usefully, you could an intermediary panel which listed every letter in the alphabet, then allow an administrator to click on one to see a list of users that begin with that name.
Writing Refiners to Filter Items
If you want to filter items from view using a refiner, you will need to write some code in SQL and/or PHP.
You can access your refiners using $this->request('refiner__my_refiner_name') in PHP, and [[REFINER__MY_REFINER_NAME]] in SQL.
You can either filter by writing a where-statement, a table-join, or both.
