In this chapter, we learned about the different types of collections, lists, and iterators, and how these can work together. We started this chapter by discussing the simplest forms of collection, ranges, and arrays. We then moved on to looking at immutable and mutable types of collections and their built-in functions. After that, we discussed different interfaces and the inheritance of these interfaces. We then talked about sets and maps and how these are different from arrays and lists. Later, we explored mutable and immutable iterators, and ended by discussing collection filters and collection functions in detail.