Haskell
In plain terms
A purely functional language with a powerful static type system.
Going deeper
Haskell enforces purity and immutability, uses lazy evaluation, and pushes side effects to the edges via constructs like monads. It's prized in academia and for correctness-critical code.
Under the hood
Laziness enables infinite data structures but complicates reasoning about performance; its type system catches many bugs at compile time.
Examples
Financial modeling, compilers, GHC, Pandoc, research and formal verification.
Think of it like...
Like mathematics turned into code: rigorous and elegant, demanding a different way of thinking.