What is the key difference between a `Structure` and an `Array` data type in ColdFusion?

The key difference between a ColdFusion `Structure` and an `Array` lies in how they store and access data: a `Structure` stores data as key-value pairs, while an `Array` stores data in a sequentially ordered list. A `Structure` is analogous to a dictionary or associative array in other programming languages; each piece of data is identified by a unique key (a string), and the value is the data itself. For example, `<cfset myStruct = CreateStruct("name", "Alice", "age", 30)>` creates a structure named `myStruct` with the key 'name' associated with the value 'Alice' and the key 'age' associated with the value 30. You access values in a structure using the key, like `myStruct.name` which would return 'Alice'. This allows for named access, making the code more readable and maintainable when you need to retrieve specific data elements.

An `Array`, on the other hand, stores data in a numbered sequence, starting from index 1 (unlike some other languages that start at 0). For example, `<cfset myArray = ArrayNew("apple", "banana", "cherry")>` creates an array named `myArray` containing three string values. You access elements in an array using their numerical index; `myArray[1]` would return 'apple', `myArray[2]` would return 'banana', and so on. Arrays are best suited for storing collections of items where the order is important and you primarily access elements by their position.

Essentially, `Structures` are designed for storing and retrieving data based on descriptive names (keys), while `Arrays` are designed for storing and retrieving data based on their position in a sequence. A `Structure` provides named access, while an `Array` provides indexed access. While both can hold multiple data items, the underlying organization and access methods are fundamentally different.