Samsung's Bada OS was launched back in 2010 and was specifically designed for touch based feature phones. Samsung's Wave was an early adopter and was praised for its spiffy and versatile operating system. It benefited from third party applications which were cultivated through Samsung's own application store.
Unfortunately, the OS featured on just a few phones as Samsung invested much of its efforts in Google's Android. However, following Google's acquisition of Samsung's direct rival, Motorola Mobility, the Korean company decided to shop for a more competent secondary OS to hedge risks.
Tizen is based on MeeGo (the OS used on Nokia's N9) and LiMo (Linux Mobile), and was created in collaboration with Intel. Samsung's gravitating towards the OS is owed to its existing loyal support and its open source versatility.
The company will begin merging existing Bada sensibilities into Tizen early this year according to a GSMArena report. The merger will no longer see Bada operate independently on mobile devices, other than the older model phones in which it is currently installed.