You've already been there... Joomla! is a great content management system. In fact it's considered one of the best in the world. But the default article system in Joomla! is so spartan! Just a title, your content body and that's it. This is where K2 comes in.
K2 was built as a complete replacement of the default article system in Joomla!. Install it like any Joomla! extension, import your articles from the default Joomla! article system and you instantly get a host of new features for your existing content: 
rich content forms for items (think of Joomla! articles with additional fields for article images, videos, podcasts & other audio files, image galleries and attachments), hassle-free image management (uploaded item images are auto-resized to 6 configurable dimensions, either globally or per category - you can now forget about using Photoshop resizing!), comments, tagging, built-in options to extend content forms (e.g. to create product catalogs), powerful content modules fetching K2 content in any way you can imagine, frontend editing with easy to use access control settings (for content-heavy websites), powerful yet easy templating (and sub-templating) for going above the "Joomla! average", extended user profiles, user groups, blogs, a powerful plugin API to extend item/category/user forms, "drag and drop" media manager and many more!
K2 is the ideal solution for managing your content, regardless of site "size": you can use it from a small blog to a complex corporate site or even a multi-author environment (portals, runnings etc.). To provide a practical example, using K2, you can transform your Joomla! website to a news/running site with author blogs, product catalogs, work portfolio, knowledge base, download/document manager, directory listing, event listing and more, all this bundled under one package! And since K2 is extensible with additional fields to its base item form, you can easily create category-specific content types, e.g. article, blog post, product page, directory listing.
It's no wonder that K2 powers some of the biggest and most popular Joomla! sites ever built worldwide!
These integrated features in K2 not only save website administrators precious management time (from managing a dozen extensions which would otherwise be required), but they also allow for better performance.
K2 was actually built on these 4 principles: feature-rich content in Joomla!, ease of use (for any type of user), flexible templating, performance
And best of all? K2 is totally free to use!
