The Suica is a prepaid e-money card for moving around and shopping. There is no more need to buy a ticket from a vending machine. Just touch your Suica to the ticket gate and the fare is automatically deducted from your Suica. The Suica can be used not only for JR East trains, but subways and buses as well.
http://www.jreast.co.jp/e/pass/suica.html