Drupal is an Open Source CMS which uses PHP for programming. It build everything from personal blogs to enterprise applications. Thousands of add-on modules and designs let you build any site you can imagine.
Drupal is free, flexible, robust and constantly being improved by hundreds of thousands of passionate people from all over the world.
Now, I am also keen to learn and working on it as I get the project from my Office which will done by using Drupal. So, I start learning and found it very simple, interactive, interesting, less code and do more, etc.
A person which is not familiar to programming can also use Drupal for web development and make some little or huge web without writing a line of code. It UI is so simple and interactive to perform task. It has a lot of module which we can also called plugins to provide cool look to the project.
On the other side, we can also create our module to make custom forms, view and other things like that. It uses function to override drupal function like hook_form() to your_module_form(). For creating module there will be two file must be in your module folder i.e. your_module.info and your_module.module. For creating database on installing your module is to create your_module.install which can your database queries.
For further info: www.drupal.org