An array is a data structure that stores a collection of elements, typically of the same type, in a fixed-size format. Each element in an array can be accessed using an index, which is a numerical value representing its position. For example, in a list of numbers, the first number is accessed with index 0, the second with index 1, and so on. Arrays are commonly used in programming to organize data efficiently. They allow for quick access and manipulation of elements, making them useful for tasks like sorting and searching. Many programming languages, such as Python, Java, and C++, support arrays as a fundamental feature.