It's no different from how you would a pull data from the database in a normal $_POST php file. All you do is use $.ajax instead.
If you're just getting data and not changing it on the server, use $.get (or $.ajax with GET) or even $.getJSON - depending on how you get your info from the server. Do not use $.post (or $.ajax with POST) unless you're making changes on the server, e.g. insert, delete or update (or changes to a file etc).