Genesis is a special theme. It is designed for developers. In itself is quite straightforward looking theme parks like WordPress, it includes a range of programmable hooks onto which developers can add or remove features. This means that the theme is highly customisable without an in-depth understanding of PHP code. That makes it very interesting to see designers. Although they still need to use PHP code snippets to make some of the changes, that is far easier than trying to write PHP code from scratch.
A range of plug-ins have also been developed for Genesis to add in additional functionality. It is also a supported theme for use with WP Types Toolset.
Many theme designers have released child themes based upon the Genesis theme framework.