Store and manage groups of values with the core Apex collection types: Lists, Sets, and Maps
Work with ordered collections of values: create lists, add and remove elements, iterate over their contents, and sort them
Store unordered collections of unique values: create sets, check membership, let a set drop duplicates for you, and compare two sets against each other
Store key and value pairs: build a map, look values up instantly by key, and walk through every key and value