To learn Drupal I've been going through the Drupal.org website and reading "Pro Drupal Development" by VanDyk and Westgate. PDD suggested that if you are a Drupal Developer you should install the Devel module.

The Devel Module is found at http://drupal.org/project/devel, and I downloaded 5.x-1.x-dev. There was also a release for Drupal 6, but I'm still on 5. I unzipped this directory, and uploaded it to my website in sites/all/modules/devel. Then in 'Home >> Administer >> Site building >> Modules' I enabled all 4 options - Devel, Generator, Devel Node Access, and Macro.

It seems that you get a bunch of DB Query Diagnostics, along with some stuff to make taxonamy easier. There is also somethign to help clear caches, which is the original reason PDD suggested installing this module.