Modules provide additional functionality to Drupal. If you are needing something that is missing, there is a chance that there's a module for that. Searching drupal.org you can find modules as simple as adding an extra type of field to modules as complex as room scheduling.
If you have identified or developed a module that you would like installed on your site, please request it by completing our online help form. Prior to installation we will evaluate the module for security and any performance concerns.