Core Java is a commonly used programming language that is considered the foundation for developing various applications and services on different platforms. It is a high-level, object-oriented programming language that enables developers to write efficient and robust code. Core Java covers the fundamental concepts of Java programming, including variables, data types, control structures, classes, objects, inheritance, polymorphism, exception handling, and more. It is widely used for building desktop, web, and mobile applications, as well as backend systems for enterprise-level software.