「後で」 means 'later'. It refers to a point in time after the present moment or after another event has concluded. It's often used when promising to do something at a subsequent time.

今(いま)から少し(すこし)経った(たった)後(あと)、または別(べつ)のことの後(あと)に行う(おこなう)ことを表します(あらわします)。