When you store data on a computer there must be a structure available in order to insert the data into. A static data structure has a fixed size. That is, it can only ever hold N amount of data elements where N is set when the structure is created. If you want to store N+1 data elements you must create a new data structure.

Let us look at an analogy. Consider a bucket, our data structure, which can hold water. A bucket can only hold so much water, or data. For example a 3L bucket can only hold 3L of water before it overflows. What happens when you want to store 4L?

Scenario 1 we just simply let the water overflow. This would result in lost water (data!). Scenario 2 we use a second, identical, bucket in order to store the extra litre of water. So one will be full while the second is only 1/3 full. Scenario 3 is where we throw the old bucket away and just simply use a bigger bucket.

Moving on from these simple analogies it is time to consider a real data structure. One of the most basic data structures is an array.