The two biggest mobile OS platforms in terms of market share are Android and iOS. Android is an open-source operating system developed by Google and is used primarily by smartphone manufacturers such as Samsung, OnePlus, and Xiaomi. On the other hand, iOS is a proprietary operating system developed by Apple exclusively for its devices such as the iPhone and iPad. Both Android and iOS have millions of apps available on their respective app stores and offer a wide range of features and functionalities for users. The choice between the two platforms often comes down to personal preference and the specific needs of the user.