An array is a collection of elements, all the same type, stored in contiguous memory. If you declare int scores[5];, you get five integer boxes sitting next to each other. Each element has an index.
The first is at index 0, the second at index 1. You access elements with scores[0] for the first, scores[1] for the second. Arrays have a fixed size set at compile time. Once you declare int scores[5];, you have exactly five elements.
You cannot add or remove elements later.