For example, if a program is using a data structure such as a list, but this data structure only allows new items to be added at one end, the resulting store will comprise data that is not ordered.

Many data structures are capable of storing multiple data items. For example, an array can store multiple data items in its various slots, and an object can store multiple data items via its fields.

Learn when and how to use different data structures and their algorithms in your own code. This is harder as a student, as the problem assignments you'll work through just won't impart this knowledge.