Kotlin is a versatile programming language primarily used for Android app development and can target various platforms, including JVM backends, native binary compilation through Kotlin/Native, and web development via Kotlin/JS. Kotlin Multiplatform Mobile (KMM) allows developers to write and reuse the same Kotlin code across Android and iOS applications, focusing on shared business logic while maintaining native user interfaces, differing from tools like Flutter and React Native that offer unified UI layers. The text details setting up a CI/CD pipeline for KMM projects using CircleCI, emphasizing the use of dynamic configuration to optimize the build process by targeting only the changed components, thereby increasing efficiency. The guide demonstrates building Android and iOS apps, each requiring specific environments, and leveraging CircleCI's dynamic config feature to streamline workflows based on codebase changes, ultimately enhancing development efficiency while utilizing KMM's multiplatform capabilities.