My (poorly informed) understanding is that the difference between "absentee ballot" and "vote by mail" is with absentee voting you must first request a ballot,

My (poorly informed) understanding is that the difference between "absentee ballot" and "vote by mail" is with absentee voting you must first request a ballot, whereas with vote by mail, they send a ballot to every registered voter. Seems pretty well the same to me, but I guess the having to request the ballot makes some people feel better about it.