Jetpack Compose is Google's modern declarative UI toolkit for Android that transforms how developers build native interfaces using pure Kotlin code instead of XML layouts. As the production standard for Android development in 2026, Compose enables reactive UIs where changes to state automatically trigger recomposition—updating only the necessary parts of the screen. The composable function paradigm (marked with @Composable) treats UI components as functions of state, making interfaces predictable, testable, and significantly easier to maintain. Understanding recomposition, state management, and modifier chains is essential—these concepts form the foundation of every Compose application and directly impact both developer productivity and runtime performance.