I believe they are referring to the lambda syntax: https://kotlinlang.org/docs/reference/lambdas.html https://kotlinlang.org/docs/reference/lambdas.html // L

I believe they are referring to the lambda syntax: https://kotlinlang.org/docs/reference/lambdas.html https://kotlinlang.org/docs/reference/lambdas.html // Lambdas are code blocks enclosed in curly braces. items.fold(0, { // When a lambda has parameters, they go first, followed by '->' acc: Int, i: Int -> print("acc = $acc, i = $i, ") val result = acc + i println("result = $result") // The last expression in a lambda is considered the return value: result })