One of the most powerful aspects of Drupal is the CCK contributed module(s). It has undergone an interesting history from its roots in the flexinode module to it's current incarnation in the form of Fields which is now part of Drupal 7 core. The functionality is simple but incredibly powerful. Fields lets you add fields (just as you might in any relational database) to Drupal which can hold data. So if you need to add a field to store the price of product you are reviewing on your Drupal site, Fields lets you do that. Further, you can then display that info