what does “::” mean in kotlin?

Question

I\'m new to Kotlin
I used this code for opening another activity:

startActivity(Intent(this,IntroAndLang::class.java))

current activity

Answer 1

Since kotlin 1.1, in addition to class, function, property and constructor references as stated above, '::' can also be used to obtain the bound references to all of the above.

For instance, using '::class' could be used to get the exact class of a particular object despite the type of the receiver as below...

val widget: Widget = ...
assert(widget is GoodWidget) { "Bad widget: ${widget::class.qualifiedName}" }

widget::class returns the exact class of the object 'widget' as either 'GoodWidget' or 'BadWidget' despite the type of the receiver expression (i.e 'Widget' as declared initially)

More info at https://kotlinlang.org/docs/reference/reflection.html