The above indicates the time span during which an action/event continues. In other words, the action/event expressed in the predicate "～" occurs throughout the time span marked by 間.
わたしは、夏休みの間、ずっと勉強するつもりです。
I plan to study throughout the whole summer vacation.
母が買い物をしている間、父は車の中で待っていました。
While my mother was shopping, my father was waiting in the car.
