Today's lesson builds off previous lessons. In previous lessons, we learned how to use the hyphen (-) when grouping sets of characters to avoid typing all characters. For example, we are able to target the letters "a" through "g" by using a hyphen in this manner, "a-g". This helps us avoid having to type in each individual character. In today's lesson, we learn that we are able to also use a hyphen when targetting numbers. This also saves us from having to type out a lot of numbers. By using a hyphen in our regular expression we are able to save time from having to write out all the characters we are matching by allowing us to use a hyphen.