I quite don't understand K2
 

Hello,

After checking out the new template Momentum, I got pretty curious about K2 and looked up K2 | The powerful content component for Joomla! developed by JoomlaWorks, watched the 4 minute video, saw the K2 demo site but I'm still not clear what K2 can be used for. The demo shows a nice template of categories for shopping and what not but was that made by K2?

Or is it basically used so that users can edit better via the front-end?

What can it be used for and how will it hurt me if I don't use it?

Thanks for your attention...