Indexing is a single arithmetic step, not a search. Because an array is a contiguous block of equal-size elements, the computer locates any element with one formula.
address = base_address + index * element_size
Give it the index and it computes the exact memory location directly. No scanning, no walking through earlier elements first. Element 0 and element 999 take exactly the same amount of work to reach.
This constant-time access is the array's headline feature. It holds no matter how large the array grows, which is why arrays back so many other structures. The one requirement is that every element be the same size, so the multiplication always lands on the right spot.
Rewriting in plainer words…
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