Welcome to our Kotlin data structures revision! Today, we will delve deeply into Kotlin Maps. Just like a library card catalog, maps enable you to quickly locate the information you need by referring to a label (key). They are vital in Kotlin for efficiently accessing values using keys, as well as for key insertion and deletion. Let's explore Kotlin's Map and MutableMap for a clearer understanding of these concepts.

Maps in Kotlin are a type of data structure that hold data as key-value pairs. They provide an efficient way to store and retrieve information based on unique keys. Each key in a map is associated with exactly one value. You can think of a map like a dictionary where you look up a word (key) to get its definition (value). Keys are unique, but values don't have to be.

Maps can be either mutable or immutable in Kotlin. Immutable maps are read-only, meaning you cannot add, remove, or modify entries once they're created. Mutable maps allow for dynamic changes, such as adding, updating, and removing key-value pairs, making them highly flexible for situations where the dataset needs to be manipulated frequently.

Here's a small example of an immutable map:

Now, let's look at an example of a PhoneBook class using a MutableMap to store contacts, allowing for dynamic changes: