Most CMS's are like a toy boat or toy truck - specific assumptions have been made about their use, assumptions it would be hard for you to override. Frameworks, on the other hand, provide you with raw materials only - you need to know a programming language, and have a clear design vision, to put them together.

Drupal is like a Lego kit. Skilled developers have already made the building blocks - in the form of contributed modules - that you need to create a site that suits your needs, whether that is a news site, an online store, a social network, blog, wiki, or something else altogether.