Seeking basic run down of php and database

[MikiHeart]

I'm trying to my hardest to change my way of coding to suit the site, but the one thing I can't seem to get a grasp of, is how all the database queries are handled.

Can someone please give me a basic run down, since we don't have any documentation(As far as I know).

$mysidia->db->select("table", array(), "thing = '$thing'")->fetchColumn();

I can assume that this part "$mysidia->db->select" is used to select the database information and so on. Instead of like "mysqli_query()", which is what I'm use to.

I don't understand why the array is there, and the "->fetchColumn()" part. I also don't understand why there is like "$result" variable after the MySql codes.

So I just need a basic run down, a little bit of help to understand, then I can start coding and working on features.

(I'm working on a few things. Like displaying a user's favourite pet in the sidebar)

Please and thank yous D=!!!