Range

Range
A Range represents an interval—a set of values with a beginning and an end.

Example Ranges
('a'..'e').to_a   #=> ["a", "b", "c", "d", "e"]

(1..5).to_a       #=> [1, 2, 3, 4, 5]

(-5..-1).to_a     #=> [-5, -4, -3, -2, -1]

(-1..-5).to_a     #=> []

Another thing to note is that you can use ... to use a range from the start but not including the end ie.

('a'...'d').to_a  #=> ["a", "b", "c"]

External Link
Ruby Docs: Range