Carrington Blog is an elegant blog-style theme with advanced features like AJAX loading of content, easy addition of analytics code, widgetized sidebars, stylish gallery features, and more. It is designed for bloggers looking for an “out of the box” experience.
Carrington JAM is a bare-bones theme skeleton. It is designed for developers as a starting point for building a new theme, it is not designed for end-users looking for a blog theme that is ready to go.