It's probably easiest to work through an example.
Take a look at the page of a typical photographers' website. Well, not so typical actually. The majority of data is highly dynamic – lots of content is only relevant to this particular offering (studio photography) and not to other offerings (schools photography for example). They want their blogs, articles, testimonials and promotions related to studio photography to show only on that page and not on other pages of the site. What's more their images are in unusual places and not in the normal page flow.
Before panels, you would have had to change Drupal's template files and write code to achieve this layout – probably a week's work. This site can be done in less than a day with Panels and Views – it's a doddle. We'd love to show you how!