Al-barzakh is the period between a person's death and his/her resurrection on the Day of Judgement. This is where souls wait before the Day of Judgement. It is also a place that divides the living from the dead.
The following video explains Al-Barzakh.
CLICK HERE to watch a collection of videos with a detailed description of Al-Barzakh by Shaykh Dr. Yasir Qadhi