to be open (e.g. a door or window), or to be held/take place (e.g. a meeting or exhibition); often seen as 開かれた / 開かれている.
市民ホールで展覧会が開かれる。
An exhibition is being held at the civic hall.
夜になっても窓が開かれているので、寒くて目が覚めた。
The window was still open at night, so I woke up because it was cold.
意見交換の場が来月開かれる予定だ。
A forum for exchanging opinions is scheduled to be held next month.