Stack engineers work on online applications employing the most up-to-date technology, frameworks, and tools. HTML, CSS, JavaScript, and React are among the technologies they use. Front-end development frameworks such as AngularJS and ReactJS are also familiar to them. Android developers are primarily concerned with creating mobile apps for Android devices. They use the Android SDK and Java to create apps that run on Android phones and tablets. They're also familiar with Android Studio and React Native, as well as other Android development tools and frameworks.