Clojure is a dynamically-typed, functional programming language that runs on the Java Virtual Machine (JVM) and embraces immutability and persistent data structures. Here are a few key features that make Clojure special:

1. Functional Programming: Clojure treats functions as first-class citizens, allowing for higher-order functions, pure functions, and immutable data structures. It encourages writing code in an immutable and declarative style, which helps eliminate many common programming errors and makes code easier to reason about.

2. Homoiconicity: Clojure's code and data are represented using the same syntax, known as S-expressions. This means that code can be manipulated as data and data can be executed as code. This makes Clojure highly extensible and enables powerful metaprogramming capabilities, such as macros.

3. Immutable Data Structures: Clojure provides a rich set of immutable data structures, such as lists, vectors, maps, and sets. These data structures are designed to be efficient and persistent, meaning that they can be efficiently shared and modified without changing the original data. This supports Clojure's emphasis on immutability and facilitates concurrent programming.

4. Seamless Java Interoperability: Clojure seamlessly interoperates with Java, allowing you to leverage the vast ecosystem of Java libraries and frameworks. Clojure can call Java code directly and vice versa, enabling easy integration with existing Java projects or utilization of specialized Java libraries.

5. Software Transactional Memory (STM): Clojure provides a built-in STM system that simplifies concurrent programming by ensuring safe and consistent access to shared mutable state. STM allows multiple threads to operate on shared data without explicit locking, reducing the complexity of writing concurrent code and avoiding common pitfalls like deadlocks.

6. REPL-driven Development: Clojure has a powerful Read-Eval-Print Loop (REPL) that allows developers to interactively experiment, evaluate expressions, and quickly iterate on code. This REPL-driven development approach promotes an iterative and exploratory coding style, making it easier to test ideas and rapidly prototype solutions.

Overall, Clojure's functional programming paradigm, immutable data structures, and seamless Java interoperability make it a unique and powerful language for building robust, scalable, and concurrent applications.