Core Java refers to the essential features and components of the Java programming language. It covers the fundamental concepts, syntax, and libraries that serve as the foundation for Java development. Core Java includes concepts like variables, data types, control structures, object-oriented programming (OOP), exception handling, and collections. Mastering Core Java is essential for building robust and scalable applications, and it forms the basis for advanced Java frameworks and technologies. Whether you're working on backend development, Android applications, or enterprise solutions, Core Java is the first step in becoming a proficient Java developer.