An Operating system (OS) is what runs a computer, and since smartphones today are handheld computers, they have an OS as well. The operating system determines which functions your smartphone can run and how its memory gets managed. The OS is also a platform that runs applications or ‘apps’.
Each OS has its own look, feel and functionalities, and the choice of which OS is best for you is mostly one of personal preference.
iOS (Apple), Android (Samsung, Sony, HTC, Huawei, Moto, LG, Alcatel) and Windows (Nokia) are the most common operating systems.