Drupal's concept explained - why the CMS is unique
One thing I've found is that newbies often don't grasp the basic concept of Drupal's structure...
Almost everything is a node of information. Nodes tend to be individual blog posts, articles, images, reviews, what have you, based on the modules installed. Flexinodes allow creating new custom node types without coding, and coding a new module is fairly trivial, thanks to a well thought out and evolving API.
Addon modules allow customizing nodes, through either adding properties (location, product sales, voting, tags, excerpt, group membership, rsvp, event time/date, eg), or adjusting module content (content filtering, display properties, permissions, pdf output, eg)
Think of it like tinkertoys: the basic concept is just spokes and hubs, but the complexity is up to you, and the choices are wide ranging. The more options you put into practice with Drupal, the more it will pay off for you in terms of a complex website that scales well.
Unlike many CMSes, there is no glass separation between modules: if your event calendar suddenly needs to be able to sell tickets to the events, just turn on the e-commerce module, tell it those events are products and you're off and running. If a blog post turns into a chapter of a book (or part of a series), just add it to that book's content, just tagging it correctly, and it'll be indexed in the correct tree, gaining navigation links as well.
Layout is very very flexible, using blocks of content, and a variety of choices of templating engines. Many Drupal sites tend to use standard layouts, but that doesn't mean yours has to look the same at all. CSS is widely used and well documented with the ability to customize almost every bit of data displayed.