A data structure is a collection of one or more variables taken as a group. Consider the storage of an inventory item. The computer needs to track the following values for each item:
Of course, the company will have many items, so these values will be stored on the disk, probably read into five arrays, and managed from there.
The problem with using separate arrays is that your code must keep track of multiple arrays for the same inventory file. It's as though you must break the single inventory file into five pieces (the arrays) while your program works with the inventory, and then combine the five arrays into a single disk file ...