It is whole program optimized, strongly typed, polymorphic, ML like language without a default evaluation order that can interact effortlessly with C and C++ code and compiles down to C++, another differentiator is the presence of coroutines
I can point to two tutorials. One explains Felix by beginning from C++ , the other describes Felix the language .
No analogies are correct, but roughly
Felix is to C++ what Scala is to JVM (or F# is to C#). Note however Felix predates all these languages.
@Ingaz the analogy is a little more literal because Felix compiles down to C++ (unlike OCaML)
But I always thought that OCaml to C++ is what F# to C#.