Indexed arrays are an appropriate data structure whenever it is natural to list items by number. In many cases, however, it is more useful to attach a non-numerical label to each item of information and refer to the information by using its label. A small predatory feline, felis felis. A medium sized mammal predator.
Dogs are highly social animals and form hunting packs.
Before the industrial era, horses were widely used for transportation and farm labor. In the Student example, the array contains biographical and administrative information for a single student. The value of the label is the actual name, or score, or whatever. The third example, Item, shows how a drill item might be represented using an associative array. Notice that many of the values in these three examples are strings.