Arrays are collections of values of the same type sequentially stored in the memory.

Arrays support the index and slice operators, which is explained in detail here.

let mut fibbonaci = [0, 1, 1, 2, 3, 5, 8, 13];
let element = fibbonaci[3];
fibbonaci[2] = 1;

There is a minor restriction for arrays at the current language state. Arrays cannot be indexed with a witness value, but only with a constant or witness-independent variable.