A list contains a collection of single objects. Maps, on the other hand, are data structures that hold collections of key value pairs. In Kotlin, there are three different types of pairs:

• Pairs of strings: <String,String>
• Pairs of ints: <Int,Int>
• Pairs of an init and a string: <Int,String>

The following is an example of a pair:

var p1 = Pair(1,"One")
var p2 = 2 to "Two"

Just like other Kotlin collections, there are two types of maps:

• Immutable maps
• Mutable maps

In this section, we will start by looking at immutable maps.