Blocks and themes
Themes are a very important aspect of every website as they create the look and feel and are expected to convey a very intuitive and user friendly presentation of the underlying functionality.
Drupal's theme layer is very flexible and powerful, among many things it is composed from a collection of web assets like CSS, JavaScript, images, and of course the HTML template layouts.
Blocks
When looking at a website, it is often very common to notice a sort of pattern that emerges in the overall website's layout. Taking the US government's white house website (http://whitehouse.gov) for example, we can break it's layout into the following parts:
The header which is at the top has to the left of it the White House's title, if so to say, along with a logo at the middle and some useful links to the right like contacting them
The horizontal menu is the main navigation area of the website, right after the header line
The middle top parts wins with image rich content and even wraps around...
