Update concepts/type-checking/about.md

Co-authored-by: Derk-Jan Karrenbeld <derk-jan+github@karrenbeld.info>

Author: quintuple-mallard

concepts/type-checking/about.md

@@ -46,7 +46,7 @@ For [historical reasons][`typeof null` is `"object"`].
 ## The `instanceof` operator
 
 For checking the type of an object, you can use the `instanceof` operator.
-It returns a boolean depending on whether the second operand is included in the first operands' [prototype chain][prototype chain].
+It evaluates into a `boolean` depending on whether the second operand is included in the first operands' [prototype chain][prototype chain].
 To clarify, `instanceof` will return whether the first operand is an instance of second operand or one of its child classes.
 `instanceof` only works for compound data types, such as arrays and objects.