Kotlin and Java are two popular programming languages used for developing Android apps, web applications, and desktop applications. Kotlin is a modern language that offers more concise and readable code, enhanced safety features, and better interoperability with Java. Java, on the other hand, has a larger community and more mature ecosystem, making it more suitable for enterprise-level projects. Kotlin is also more suitable for mobile app development, whereas Java is more versatile and can be used for a wide range of applications. Ultimately, the choice between Kotlin and Java depends on the project requirements, the developer's skillset, and personal preference.