Understanding of '_' (underscore) in Scala as a type variable

Question

In Scala I can use underscore as a type variable in function, for instance.

  def fun[_, _]() = {
    // ?
  }

  fun[Int, String]()

Is it so useful in real life programming? How could it be useful for me?

Answer 1

Is it so useful in real life programming?

No, it isn't.

How could it be useful for me?

To confuse people. You could theoretically use it to mark an unused type parameter when e.g. overriding a method, but I don't think I've ever seen this.