Haskell is a purely functional programming language known for its strong type system, immutability, and emphasis on declarative programming. It supports lazy evaluation, allowing computations to be deferred until needed, and encourages writing concise, elegant code. Haskell is often used in academic, research, and high-performance computing contexts due to its ability to express complex ideas clearly and its robust support for concurrency and parallelism. Its strong type inference and mathematical foundations make it well-suited for building reliable, scalable software systems.