When looping through a collection of items, we sometimes want access to the index of an item at each iteration.
We can do that with collection.each_with_index{ |item, index| ... }.
In this case, index will always start at 0.
If we want index to start from a particular number, we can use Enumerator#with_index and specify an offset.
For example: collection.each.with_index(1){ |item, index| ... }.