Barzakh (Arabic: برزخ From Persian برزخ (barzax)) is an Arabic word meaning "obstacle", "hindrance", "separation", or "barrier". In Islamic eschatology, although largely up to interpretation, al-Barzakh is generally viewed as the barrier between the physical and spiritual worlds, in which the soul awaits after death and before resurrection on Qiyamah (Judgement Day).
Barzakh is mentioned only three times in the Qur'an, and just once specifically as the barrier between the corporeal and ethereal, as a place in which, after death, the spirit is separate from the body, freed to contemplate the wrongdoings of its former life. Despite the gain of recognizance, it cannot utilize action. The other two occurrences refer to Barzakh as an impassable barrier between fresh and salt water. While fresh and salt water may intermingle, an ocean remains distinct from a river. Pertaining to Al-Barzakh, this notion implies that although the physical and spiritual realms are distinctly separate, transmigration through Al-Barzakh between the two is possible, as later expanded by Sufi mystics.
In Hadith, Ibn al-Qayyim cites that, albeit not mentioned in the Qur'an, souls in Al-Barzakh would be grouped with others matching in purity or impurity.
In Islam, the soul and the body are dependent upon each other. This is significant in Barzakh, because only a person's soul goes to Barzakh and not their physical bodies. Since one's soul is divorced from their body in Barzakh, the belief is that no progress or improvements to one's past life can be made. If a person experienced a life of sin and worldly pleasures, one cannot try to perform good deeds in order to reach Jannah. Whatever one does in his or her lifetime is final and cannot be changed or altered in Barzakh.
The idea of purgatory is that it is a place where people go after death that holds punishment and purification for those who are not fit to enter Paradise just yet. People who are in this place do not have enough sins to warrant their entrance into Hell, but they do not have enough good deeds to go to Paradise. This is a temporary place, similar to barzakh. Because they have this in common, some believe that they are the same idea or concept. Barzakh is actually closer to the idea of limbo, a place that is between life and the true afterlife. In this place, people await their final judgment, much like in barzakh. The Quranic idea of aʿrāf or “heights” is closer to that of Christian purgatory. Aʿrāf is also thought of as a place where souls go whose good and bad deeds are too evenly matched to go directly to Paradise or the Fire.