Type alias allows you to create an alias for any Type. Why would we want to create another name for Int or String? Its all about readability Consider that you are storing a time, or a currency amount? In java days we would store them:
String amount = 250 Int elapsedTime = 120
How do we know if that amount is mean to represent cents or dollars? Does that time represent 2 minutes, 2 hours or 120ms? We can make this a lot more readable in kotlin with the use of typealias
typealias Cents = Int fun Cents.asDollars(): Float = this.toFloat()/100
typealias Seconds = Int fun Seconds.asMinutes(): Float = this.toFloat()/60
amount: Cents = 250 elapsedTime: Seconds = 120
Now it is really readable, the amount is 250c or asDollars() 2.50 and the time is 120 seconds to asMinutes(), 2.
Underneath the hood, the compiler treats all these as Ints, so there is no performance issues, but readability is greatly improved.
