iOS is what makes Apple’s mobile devices or, "iDevices", turn on and run all the stuff you want to do with it. Its the basic "operating system" that operates any given iDevice. Apple’s portable devices like iPhone, iPad or iPod are know as iDevices
iOS does things on these devices such as allow you to set the brightness of the screen if you can’t see it on a bright sunny day, it also secures your iDevice, if you enter a pass code the system will automatically lock the screen after a certain amount of minutes you tell it to and lets you connect to your WiFi network at home so you can go online with your iDevice.
what we need to learn to go
The most basic building block of Android development is the programming language Java. To be a successful Android developer, you’ll need to be comfortable with Java concepts like loops, lists, variables, and control structures.
You’ll also need to learn the basics of SQL in order to organize the databases within Android apps. SQL is a language for expressing queries to retrieve information from to databases.
Android Software Development Kit (SDK) and Android Studio
One of the best parts about developing for Android is that the necessary tools are free and easy to obtain. The Android SDK is available via free-of-charge download, as is Android Studio, the official integrated development environment (IDE) for Android app development.
Programmers use XML to describe data. The basics of the XML syntax will be helpful in your journey to full-fledged Android developer in doing tasks like designing user interface (UI) layouts and parsing data feeds from the internet.