At least that's what it seemed to me.
NOOBS (New Out Of The Boot Software), is a new way to copy the operating system on an SD. We copy the software image on the SD-card, and once started you must to select the operating system you want to install. You also have option to configure the config.txt. But you get more...
If you get bored and want to install another (removing the previous one, is what differentiates you from Berryboot), press SHIFT during boot process and we have the option to install another operating system again.
The method is created to make it easier to install the various SO, especially for kids.
Link: Quick start guide - pdf