Answer 1

It is an iterable collection of same-type elements, for example:
[1, 2, 3, 4]
['d', 'fht', '47']

It can be one-dimensional, like the two above or two- or multi-dimensional (array of arrays of arrays...). Like this (a 2D, 3x3 array):
[[1, 0, 1],
[0, 1, 0],
[1, 0, 1]]

Depending on a language, they are mutable (you can update its values and size) or partially mutable (only values can be updated, but not the size).