All humans have a soul and when we die the souls will go to Heaven or to Hell or they will temporary go to Purgatory to walk towards the Skies.
The Souls of Purgatory
It is not possible to invoke nor to evoke souls nor calling back the dead, this is a divination practice used in spiritualism or in other practice linked with Satanism, but we have to allow God to place things in the best way, in His sovereignty. So, God can allow some souls asking help to their brothers on Heart, in His sovereignty, goodness and mercy. We cannot evoke these visits, but we have to respect them and answer to their helping requests, offering especially a Holy Mass.
The Holy Church does not oblige to believe in private apparitions, as they do not add any new truth about faith. If a soul of Purgatory visits us or not, this does not change our faith, by the way, it is a big mistake despising the manifestations of the Sky and Purgatory without a reason.
Holy Souls, with their apparitions, they always look for good: they promote catechesis, increase fervour and devotion, they increase love for the Holy Communion, they form our lives to prayer, to the practice of charity, they invite to control our defects and destroy vices through confession and conversion.
Generally, Holy Souls have visited pitiful people or who where walking towards sanctity. Among people receiving visits from the Holy Souls, there are: Saint Gemma Galgani, Pope Gregorio Magno, Saint Brigida of Sweden, Saint Caterina of Genova, Saint Faustina and many others. It is impossible to deny the witnesses accepted by the Church.
There are psychological and emotional circumstances that, for the big moral woe, could make we believe, owing to autosuggestion or deep emotion, in the visits of our dear dead. Neither, we have to label this visits as fraudulent or unexplainable by the pure psychology; denying his liberty of appearing owing to God’s permission. Saint Teresa of Avila, lady of great sensibleness and realism, recognized by the Church as Doctor, told that Saint Pedro of Alcantare visited her after his death to tell her that he will go to Heaven.
Holy Scriptures do not tell every about the Holy Catholic Church FAITH. But the Bible should be interpreted together with the Apostolic Tradition. The Church, guided by the Holy Spirit, as Jesus Christ promised, recognise the authenticity of some mystic experiences and the teachings of those who are canonized as Saints. Denying it will be like denying the Church the right of canonize and beatify, and fortify the truthfulness of such mystic experiences.
Jesus in the Gospel told the case of the rich Epulone and the poor Lazarus. In this story the visit of the dead Lazarus to the Earth it is asked by the rich Epulone, who is in Hell. We can see that Souls are under God’s authority and in this case He deny the visit.