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

@@ -74,7 +74,7 @@ The `Array` class has a method called `Array.isArray()` that checks if its argum
 
 While `instanceof Array` will not work with an array created in a different realm such as an `iframe` in a webpage, `Array.isArray()` will.
 
-This is because the Array class has a different constructor in each `iframe`, meaning that the function in the prototype chain will be different, causing `instanceof Array` to fail.
+This is because the Array class has a different constructor in each realm, and each `iframe` has its own ream, meaning that the function in the prototype chain will be different, causing `instanceof Array` to fail.
 `Array.isArray()` is capable of ignoring this, and should always be used when possible.
 ```