Data Structure Guide
Data Structures in Programming
A data structure is a programming construct that contains data while your game is running.
An array is a data structure that is similar to a variable and has a number of elements, or "slots". While a variable is like a box that can hold one value, an array is like having multiple boxes to hold a piece of information in each slot. As a rule of thumb, an array must be of the same data type. You can not combine e.g. integers and strings in a single array.
Dim is short for dimension and is used to declare arrays and types.