Drupal Modules:

A Drupal site can have three kinds of modules: core modules that ship with Drupal and are approved by the core developers and the community; contributed modules written by the Drupal community and shared under the same GNU Public License (GPL) as Drupal; and custom modules created by the developer of the website. This section of the Developing for Drupal handbook will help you to write your own modules and to collaborate with the community on shared projects.

Theme Module:

The Content Template (a.k.a. ConTemplate) module allows modification of Drupal's teaser and body fields using administrator defined templates. These templates use PHP code and all of the node object variables are available for use in the template.Templates are normally stored in the database but it is also possible to create disk-based templates which live in your sites directory and can be inherited across multisite installations in the same way as themes or modules.

Customized Modules:

Drupal Web Developers has extensive experience with creating custom designs for sites using content management systems and Drupal is no exception. With Drupal Web Developers you can choose from any number of preexisting themes, or our designers can create a custom Drupal theme that reflects your branding and message requirements.In addition to custom Drupal themes Drupal Customized Modules can also help you determine the best Drupal modules to include to reach your business goals.

Drupal Installation Module:

Once you have the Drupal core files installed, you can begin adding third-party contributed modules to extend or alter Drupal's behavior.
The basic drupal module instruction steps are

Download the module
Extract the files
Upload the folder at specific path
Enable the module
Enable Module dependency
Set file permissions
Module configuration