The document discusses arrays in C++. It defines arrays as collections of data of the same type used to store multiple values. Arrays are declared with a type followed by brackets containing the number of elements, such as int score[5]. Indexed elements can be accessed using subscript notation like score[0]. Arrays can be passed to functions as arguments. Functions can process the entire array but do not know its size, so a size parameter is typically included. Arrays cannot be returned from functions.