‘Barzakh’ is a world between this world and the afterlife. It is also called the imagine world or the world of grave. Barzakh exist for both believers and non-believers, though it is like the Hell for non-believers.
Meaning of ‘Barzakh’
‘Barzakh’ in Arabic literally means an interval or barrier between two things, and in the Islamic terminology, it means an interval between the end of this worldly life (death) and the beginning of afterlife. The world is called ‘Barzakh’ because it is an interval between this world and afterlife. The world is also called the world of grave and the imaginable world. The ‘Barzakh’ is one of the phases or stages through which every soul will pass through before the Day of Judgement.
Barzakh in the Qur’an
The concept of Barzakh has been mentioned in the Holy Qur’an thus, "Haply I may do good in that which I have left. By no means! It is a (mere) word that he speaks; and before them is a barrier until the day they are raised”. 
According to the verse and its preceding one, the request of some people at the deathbed of returning to the world in order to do good acts that have not been done while they are in this world is not in place, and they face a barrier or an interval –a Barzakh- until the Dooms’ Day. The phrases "until the day they will be resurrected” indicate that Barzakh is an interval between this world and the afterlife that the souls experience after their death and before the Day of Resurrection.
Likewise, in another verse of the Qur’an, it is said: "Between them is a barrier which they cannot pass”. 
This barrier separates the ephemeral life from the real and everlasting one that is awaiting us. Rather, it is one of its stages or a station, which every soul shall experience before the final resurrection. In ‘Safeenat al-Bihar’, Imam as-Sadiq (AS) was reported saying: "By Allah, I fear for you the Barzakh. He was asked: "What is the Barzakh?" He said: "It is the grave from the moment of death till the Day of Judgment." 
However, a question that comes to mind at this juncture is that "Is the ‘Barzakh’ similar to the purgatory of the Catholic Christians?” The Catholics believe that the purgatory is a place where the souls of the dead are cleansed before receiving God's grace, and such cleansing includes atonement through pain. This seems to be close to the Islamic concept because the Almighty punishes many of His servants in the grave in order to attain justice. However, the cleansing does not apply to everyone. It involved only selected sinners who are to be punished in this life, in the grave and in the Hell as well. However, the "purging" in which the Catholics believe may be close to the "grave's constriction". It is stated in some traditions that this constriction, or the torment in the grave, is one of the manifestations of the Justice of the Almighty, Who does not wish to torment His servants twice; so, the grave is the last stage where such people have to "pay" for some of their sins.
Meanwhile, for any sane person, it is better, of course, to avoid such torment by doing some things in this life that will guaranteed one’s safety. One of such acts, according to some traditions include recitation of supplications on a regular basis and rendering moral and financial assistance to others who are in needs.
In the book ‘Jami` al-Akhbar’, the following is documented:
A companion reported the Holy Prophet (PBUH) as saying: "Send your gifts to your dead." He was asked about what gifts could be sent to the dead, so he said, "Charity and supplication."
Punishment in Barzakh
The ‘Barzakh’ is a place of joy and … for the faithful ones and it is a point of chastisement for the sinners as well. One of such sins, which qualify one for the punishment in the ‘Barzakh’, is non-fulfilment of the rights of others. It is mentioned in the book of ‘Misbahul Harmain’ that in the last days of his life, a respected personality named Shaykh Abdul-Tahir Khorasani travelled to Mecca and he made a vow to serve the Holy house (i.e. Ka’abah) as long as he was alive. During those days, a person with a bag full of gems, jewels and money was looking for a reliable person who may hold it as a trust. People suggested the name of Shaykh Abdul-Tahir Khorasani as one of the most reliable and honest personalities in Mecca. Thus, the man thereafter placed his trust with the Shaykh. After a period of time, the Shaykh passed away. On the return of the man, he was informed of the Shaykh’s dead. So, he approached the successors of the Shaykh but they expressed ignorance of the matter. The man was devastated and he was reduced to penury due to this. However, the man was aware of the fact that the souls of the believers arrive in ‘Wadi’u-s-Salaam’ and that they are free and communicate with one another. So he prayed to the Almighty Allah to enable him to see the deceased so that he can ask him about his money.
After a long time, when he did not get any reply from the valley, he inquired from some contemporary scholars why he was not getting any reply from the Shaykh. They told him that it was possible that the Shaykh might be among the wrongdoers. That is, he might be in ‘Wadi Barhut’, which is in Yemen. ‘Wadi Barhut’ is a dangerous valley having horrible wells etc. It is often mentioned that extremely terrifying voices are heard in that place. In other words, in the same way ‘Wadiu-s-Salaam’ in the neighborhood of Amir al-Mu’mineen (A.S) was a place of peace and safety for noble souls, the ‘Wadi Barhut’ was a place of stay for wicked souls.
In any case, the man set out for the ‘Wadi Barhut’ and became engrossed in prayer, fasting and supplications until one day, he saw Shaykh Abdul-Tahir. He asked: Are you, Abdul-Tahir? Yes, replied the Shaykh. But are you not the one who served the Holy shrine in Mecca? Yes, said the Shaykh. That person asked about his bag and why the Shaykh was in such a bad condition. The Shaykh said: "Your trust is buried in such and such corner of the house. You did not come to collect it for such a long time, so I could not return it to you before my death. Now you may go there and direct my survivors to restore your trust”. The Shaykh added, as for your question on my bad condition; you should know that it is due to three sins: One is rights of others, which are like a rock attached to the wing of a bird that does not allow it to fly away. Such is the seriousness of this matter that even though a person might have performed the Ziyarat of Karbala, Mashhad or served at holy Ka’abah, he cannot get the neighborhood of Ahlul-Bayt (A.S) if he has not observed this properly. No matter where the body of that person might be buried; in Mecca, Medina or ‘Wadiu s-Salaam’, it would not be allowed to proceed to the high Heavens if it has not fulfilled the rights of others. The three sins that are responsible for the state I am are as follow:
1. The first sin, which I was reminded, is that I had cut off relations from my relatives in Khorasan and travelled to settle down in Mecca. It is prohibited to severe relations and not paying attention to the tribe and community to which one belongs. There are so many people, who do not pay for the obligatory expenses of their children and parents. In addition, they do not care even if they are involved in some difficulties. They settle down in some other towns and do not pay any heed to their condition and well-being.
2. The second sin was that I had given a ‘Dinar’ to an undeserving person. The statement of the book is as follows: "Perhaps one ‘Dinar’ was not given to a deserving person, instead it was given to an undeserving person and it is unlawful to deprive a deserving fellow”.
3. The third sin was that a scholar of religion resided in our neighborhood, and we caused insult to him. The scholar is having a right upon us and we learn about our religion from him. The scholar is having rights upon the society. The Messenger of Allah (PBUH) was reported to have said that one who insults a scholar is as if he has insulted me. Thus, if one is not attentive and has caused insult to a scholar or had been rude to him, it is as if he has denied the rights of the scholar and he would be answerable for that.
O God, what shall we do if You were to deal with us with Your justice?
O God, we are indeed fearful of Your justice.
O God, deal with us with mercy and grace; for we are not having the capacity to bear Your justice. O the Most Merciful of the merciful ones.
To be continued Insha’Allah in the next edition