There's not much of a difference between Early Decision 1 and Early Decision 2 - except for the timing. Students that know that they have a first choice school, and will go regardless of being accepted elsewhere, have the opportunity to apply a bit earlier. The timing for these 2 rounds are different with Early Decision 2 deadlines closer to the deadlines of Regular Decisions, but that the notification of Early Decision candidates is typically in February instead of late March/April.
Here's a list of schools with the option to submit and Early Decision 2 (ED2) application:
College, Graduate School, and Career Coaching.