The word literally means out of communion, or no longer in communion. In some churches, excommunication includes the belief that the person who was exocommunicated is going to Hell. Sometimes punishment follow excommunication; these include being banned, shunning, and shaming, depending on the group's religion or religious community.
Plaque on exterior of the Chiesa della Pietà in Venice, the church of the orphanage. This is where the foundling wheel once stood. The inscription declares, citing a 12 November 1548 papal bull of Pope Paul III, that God inflicts "maledictions and excommunications" on all who abandon a child of theirs whom they have the means to rear, and that they cannot be absolved unless they first refund all expenses incurred.
Excommunication for Kids. Kiddle Encyclopedia.