Calling values in a multidimensional array?

I'm stuck on this problem:

s = [["dog", "bark"], ["cat", "meow"], ["sheep", "baa"]]

s.each do |x|
  x.each do |y|
   puts y
end
end

What is happening in the code here? I normally can visualize and depict what happens in a do/end but with this array I'm not sure.

1) Why don't I have to use brackets to call values in the array? I want to call only the the type of animal which is the first value or the array[0]. Then I want to call the second value, the sound the animal makes. I know that the values start with 0 when calling the array.

2) s.each do |x| - is this reading the whole array? or only the first value?

3) x.each do |y| - is this reading the first value? it must be because the y value is what is in puts and that is result I am looking for.

4) How does it know how to do this from |x| and |y|. It isn't like in the array that the values are labeled or defined as x and y ever. I think they would be [0] of the array and [1] of the array and brackets are never even used to call upon values in the array?

My code spits this out:

dog bark cat meow sheep baa

Any insight would greatly appreciated. Thanks!