Wikipedia
F# (pronounced F sharp) is a strongly typed, multi-paradigm programming language that encompasses functional, imperative, and object-oriented programming techniques. F# is most often used as a cross-platform CLI language, but can also be used to generate JavaScript and GPU code.
F# is developed by the F# Software Foundation, Microsoft and open contributors. An open source, cross-platform compiler for F# is available from the F# Software Foundation. F# is also a fully supported language in Visual Studio and Xamarin Studio. Other tools supporting F# development include Mono, MonoDevelop, SharpDevelop, MBrace and WebSharper. Plugins supporting F# exist for a number of widely used editors, most notably the Ionide extension for Atom and Visual Studio Code, as well as integrations for other editors such as Vim, Emacs or Sublime Text.
F# originated as .NET implementation of a core of the OCaml programming language, and has also been influenced by C#, Python, Haskell, Scala and Erlang.