JShell is an interactive tool introduced in Java 9 that allows developers to execute Java code snippets in real-time. It provides a command-line interface where users can quickly test code, explore APIs, and experiment with Java features without the need to create a full application. With JShell, programmers can write and evaluate expressions, define methods, and create classes on the fly. This makes it a valuable resource for learning, debugging, and prototyping, as it simplifies the process of trying out new ideas and understanding how different parts of the Java language work together.