What is WBDB and what does it allow me to do in WordPress when using it?
WPDB - WordPress Database
WPDB is a class within the WordPress Core, created to allow the communication between both the WordPress website and its database.
By using $wbdp, it allows you to run most of the standard SQL queries in order to SELECT, INSERT, REPLACE, UPDATE or DELETE data from the WordPress Database accordingly.
Tip: when using $wpdb, you should globalise the variable first by defining global $wpdb; at the top of your file or function.