Kotlin is a statically-typed programming language that runs on the Java Virtual Machine and also can be compiled to JavaScript source code. wikipedia.org

Android is an operating system based on the Linux kernel with a user interface based on direct manipulation, designed primarily for touchscreen mobile devices such as smartphones and tablet computers. wikipedia.org

Is a platform for web and mobile application. wikipedia.org

WebRTC (Web Real-Time Communication) is an API definition drafted by the World Wide Web Consortium (W3C) that supports browser-to-browser applications for voice calling, video chat, and P2P file sharing without the need of either internal or external plugins.

The Google Maps API allows developers to embed dynamic, draggable maps in their web applications. It's free for sites that are freely available to the public, and there's an enterprise version for private sites.

Java is a programming language and a core component of Oracle Corporation's Java Platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. wikipedia.org

Web development is a broad term for the work involved in developing a web site for the Internet (World Wide Web) or an intranet (a private network).

iOS (formerly iPhone OS) is Apple Inc.'s mobile operating system. Originally developed for the iPhone, it has since been extended to support other Apple, Inc. devices such as the iPod Touch, iPad, and Apple TV. wikipedia.org

A payment gateway is an e-commerce application service provider service that authorizes payments for e-businesses, online retailers, bricks and clicks, or traditional brick and mortar. wikipedia.org