In the broadest sense Android and IOS are similar to browsers: All are platforms that execute code given in a certain format and have APIs for interacting with the device.
(The browser is different in that it doesn't need a separate download to acquire the code and makes partial code downloads easy. And from search to opening an app is a single click and very quick.)
(The browser is different in that it doesn't need a separate download to acquire the code and makes partial code downloads easy. And from search to opening an app is a single click and very quick.)