iOS is the operating system at the heart of Apple's iPhone and iPad mobile devices. Unlike Google's Android operating system, iOS runs apps natively without a virtual machine environment. All development is done in the freely available Xcode application that requires a workstation running the OSX operating system and an Apple Developer License to compile and deploy to iOS devices.
Apple's mobile application ecosystem is much more tightly managed than Android, and all apps must undergo a two week review before they will be made available for download from the App Store. This can be an issue for projects that are on a tight timeline, and planning around it is key. Developers can deploy the app locally to devices they have physical access to, but distribution to remote locations must be handled through Apple's Testflight service. This can make User Acceptance Testing more complicated than it is on Android devices.
Development work done for iOS is not cross-compatible with Android devices. If your project is targeting both Android and Apple with a native application, you will need to develop two distinct products. While this will allow you to access the most amount of functionality and performance from iOS devices, not all projects may need this level of optimization. In these scenarios we recommend considering a cross-platform development framework.
We like Apache's Cordova project that gives developers the tools to write a single, cross-platform application that can be published to both Android and Apple devices. Toolsets built with Cordova, like Quasar and Ionic, can help your project get a headstart with a collection of open source projects designed to work together to give you a mobile application built on top of the Webview object common to both mobile ecosystems. This allows developers to build or port an existing web application to the App Store and Google Play Store.